JP2009238903A - Semiconductor device, and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device can improve injection efficiency of charge into a charge storage layer; and a manufacturing method of the same. <P>SOLUTION: This manufacturing method of the semiconductor device provided with a first insulation film formed on a semiconductor substrate, the charge storage layer formed on the first insulation film, a second insulation film formed on the charge storage layer, and a control gate electrode formed on the second insulation film includes processes of: forming the first insulation film 204; forming a lower insulation layer 201; forming a germanium-containing layer 202 on the lower insulation layer 201; forming an intermediate insulation layer 202a by reaction among the germanium-containing layer 202, silicon and oxygen; and forming an upper insulation layer 203 on the intermediate insulation layer 202a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a semiconductor device and a manufacturing method thereof.

  A nonvolatile semiconductor memory device typified by a NAND type memory includes a tunnel insulating film formed on a semiconductor substrate, a floating gate electrode formed on the tunnel insulating film, and an interelectrode insulation formed on the floating gate electrode. And a control gate electrode formed on the interelectrode insulating film (see, for example, Patent Document 1).

  In a nonvolatile semiconductor memory device having a floating gate electrode, the potential of the floating gate electrode is controlled through capacitive coupling between the floating gate electrode and the control gate electrode by controlling the potential of the control gate electrode. When the semiconductor substrate is grounded, the potential Vfg of the floating gate electrode is obtained by using the capacitance C1 between the floating gate electrode and the control gate electrode, the capacitance C2 between the floating gate electrode and the semiconductor substrate, and the voltage Vcg of the control gate electrode. It is expressed as C1 / (C1 + C2) × Vcg.

  Here, C1 / (C1 + C2) is called a coupling ratio. The control gate voltage required to obtain a certain floating gate voltage required for the rewrite operation is in an inversely proportional relationship with the coupling ratio.

  In a nonvolatile semiconductor memory device, a high voltage is generally required as a rewrite voltage. However, since the voltage applied to the tunnel insulating film is based on the coupling ratio, a large voltage must be applied to the control gate electrode. As the device structure is further miniaturized in the future, a parasitic capacitance (α) is generated between adjacent memory cells, and the coupling ratio is expressed as Vfg = C1 / (C1 + C2 + α) × Vcg. And a higher voltage needs to be applied to the control gate electrode.

However, if the control gate voltage is simply increased in order to obtain a certain floating gate voltage necessary for the rewrite operation, the insulating film is rapidly deteriorated, causing dielectric breakdown, an increase in leakage current, and a decrease in reliability. Therefore, it is necessary to improve the charge injection efficiency into the charge storage layer such as the floating gate electrode and reduce the rewrite voltage.
Japanese Patent Laid-Open No. 9-134973

  An object of the present invention is to provide a semiconductor device capable of improving charge injection efficiency into a charge storage layer and a method for manufacturing the same.

  A manufacturing method of a semiconductor device according to a first aspect of the present invention includes a first insulating film formed on a semiconductor substrate, a charge storage layer formed on the first insulating film, and the charge storage layer. A method for manufacturing a semiconductor device, comprising: a second insulating film formed thereon; and a control gate electrode formed on the second insulating film, wherein the first insulating film is formed. A step of forming a lower insulating layer containing silicon and oxygen as main components, a step of forming a germanium-containing layer containing germanium as a main component on the lower insulating layer, the germanium-containing layer, silicon and oxygen A step of forming an intermediate insulating layer containing silicon, germanium and oxygen as main components, and a step of forming an upper insulating layer containing silicon and oxygen as main components on the intermediate insulating layer. Characterized in that it comprises a.

  A semiconductor device according to a second aspect of the present invention includes a first insulating film formed on a semiconductor substrate, a charge storage layer formed on the first insulating film, and formed on the charge storage layer. And a control gate electrode formed on the second insulating film, wherein the first insulating film contains silicon and oxygen as main components. A lower insulating layer, an intermediate insulating layer formed on the lower insulating layer and containing silicon, germanium and oxygen as main components, and an upper layer formed on the intermediate insulating layer and containing silicon and oxygen as main components And an insulating layer.

  According to the present invention, the efficiency of charge injection into the charge storage layer can be improved.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view schematically showing a configuration of a semiconductor device according to the first embodiment of the present invention. 1A is a cross-sectional view along the channel length direction (bit line direction), and FIG. 1B is a cross-sectional view along the channel width direction (word line direction).

  As shown in FIG. 1, the nonvolatile semiconductor memory device according to this embodiment includes a semiconductor substrate (silicon substrate) 100, a tunnel insulating film (first insulating film) 103 provided on the semiconductor substrate 100, and a tunnel. Formed on the floating gate electrode (charge storage layer) 104 provided on the insulating film 103, the interelectrode insulating film (second insulating film) 105 provided on the floating gate electrode 104, and the interelectrode insulating film 105 The control gate electrode 106 is provided.

  In the element region of the semiconductor substrate 100, a source / drain region 101 and a channel formation region 102 sandwiched between the source / drain regions 101 are provided. An element isolation region 107 having an STI (Shallow Trench Isolation) structure formed of a silicon oxide film is formed around the element region.

  As will be described later, the tunnel insulating film 103 includes a layer containing silicon, germanium, and oxygen as main components.

  Next, a method for forming a tunnel insulating film according to the present embodiment will be described with reference to FIG.

First, as shown in FIG. 2A, a silicon oxide film (lower insulating layer) 201 having a thickness of 4 nm or less is formed on a semiconductor substrate (silicon substrate) 200 by, for example, heat treatment in an oxidizing atmosphere. For example, oxygen (O ₂ ) gas is used as an oxidizing agent, and oxidation is performed under conditions of a temperature of 900 to 1000 ° C. and a pressure of 400 to 760 Torr. Further, ozone, oxygen, water vapor, oxygen radicals, oxygen ions, hydroxide ions, or hydrogen group radicals may be used as the oxidizing agent. In order to obtain a high-quality silicon oxide film with few defects, the heat treatment condition is preferably a high temperature condition of 900 ° C. or higher, but may be a temperature of 900 ° C. or lower. Further, after forming the silicon oxide film 201, nitrogen may be introduced into the silicon oxide film 201 by thermal nitridation or the like.

Next, a raw material gas containing germanium hydride (GeH ₄ ) is introduced into a reaction vessel having a temperature of 400 to 500 ° C. and a pressure of several tens to 200 Torr. As a result, a germanium layer (germanium-containing layer containing germanium as a main component) 202 having a thickness of about 2 nm is deposited on the silicon oxide film 201 as shown in FIG. The thickness of the germanium layer 202 is desirably thin, and typically 2 nm or less.

  Thereafter, as shown in FIG. 2C, TEOS and ozone gas are introduced onto the germanium layer 202 into a reaction vessel having a temperature of 500 to 700 ° C. and a pressure of 10 to 100 Torr, for example. That is, a gas containing silicon and oxygen is introduced. Thereby, the silicon oxide film 203 (upper insulating layer) is formed by CVD (Chemical Vapor Deposition). Prior to the formation of the silicon oxide film 203, the germanium layer 202 reacts with silicon and oxygen contained in TEOS and ozone gas to form a layer (intermediate insulating layer) 202a containing silicon, germanium, and oxygen as main components. The Hereinafter, for convenience, this layer is referred to as a silicon germanium oxide layer. At this time, it is desirable that the entire germanium layer 202 is converted into the silicon germanium oxide layer 202a. In this step, the CVD method is used to form the silicon oxide film 203, but an ALD (Atomic Layer Deposition) method may be used. Furthermore, a chemical sputtering method in an oxidizing atmosphere, a high temperature coating method of about 400 ° C. or higher, or the like may be used. In this way, a tunnel insulating film 204 having a silicon oxide film (lower insulating layer) 201, a silicon germanium oxide layer (intermediate insulating layer) 202a, and a silicon oxide film (upper insulating layer) 203 is formed.

  According to the above embodiment, the silicon germanium oxide layer 202a is formed in the tunnel insulating film 204 in a region within 4 nm from the surface of the semiconductor substrate 200, for example. Therefore, a charge trap level (charge assist level) having a shallow energy level due to the silicon germanium oxide is formed in the tunnel insulating film 204. That is, a level that assists the movement of electrons injected from the semiconductor substrate 200 is formed in the vicinity of the interface of the semiconductor substrate 200 in the tunnel insulating film 204. As a result, the injection efficiency of electrons injected from the semiconductor substrate 200 into the floating gate electrode through the tunnel insulating film 204 is improved when a high electric field is applied in the data write operation.

  Note that the charge assist level based on silicon germanium oxide does not assist the movement of electrons when a low electric field is applied in a data read operation. As a result, the charge retention characteristics of the nonvolatile semiconductor memory device of this embodiment are not reduced.

  Note that germanium in the germanium layer has a large diffusion coefficient, and germanium in the silicon germanium oxide layer has a small diffusion coefficient. For this reason, when germanium is converted into silicon germanium oxide as in the present embodiment, it is possible to further suppress the diffusion of germanium due to heat treatment when the silicon oxide film 203 is formed. As a result, the collapse of the germanium distribution in the tunnel insulating film 204 is suppressed. Therefore, low electric field leakage can be reduced, and deterioration of electrical characteristics such as charge injection efficiency and charge retention characteristics can be suppressed.

  In the tunnel insulating film 204 in the present embodiment, a silicon oxide film is formed as a lower insulating layer and an upper insulating layer of the tunnel insulating film 204. However, an insulating film containing silicon and oxygen as main components can be used as a lower insulating layer and an upper insulating layer of the tunnel insulating film 204. For example, the silicon oxide film may contain nitrogen.

(Modification)
Next, a modification of this embodiment will be described.

  The basic structure and the basic manufacturing method are the same as those in the first embodiment. Therefore, the description about the matter demonstrated in 1st Embodiment and the matter which can be easily guessed from 1st Embodiment is abbreviate | omitted.

  In this modification, the pressure in the reaction vessel is set to a low pressure of, for example, 1 Torr or less when the germanium layer 202 is formed. In this manner, the germanium hydride partial pressure is lowered to form the germanium layer 202.

  Since germanium hydride has a low surface adsorption probability, it is likely to migrate and nucleate. For this reason, the flatness of the surface of the germanium layer 202 is deteriorated. However, by reducing the germanium hydride partial pressure, nucleation can be suppressed, and a germanium layer with high flatness can be formed in a region within 4 nm from the surface of the semiconductor substrate 200. As a result, the flatness of the tunnel insulating film 204 is improved, so that the leakage current density of the tunnel insulating film 204 in the low electric field region can be further reduced and the charge retention characteristics can be further improved.

Note that germanium hydride gas, an inert gas such as Ar or N _2, or hydrogen gas may be mixed and introduced into the reaction vessel. In this case, the total pressure can be increased to 10 to 100 Torr to ensure the stability of the film formation process, and the germanium hydride gas partial pressure can be reduced to improve the flatness of the tunnel insulating film 204.

(Second Embodiment)
Next, a tunnel insulating film forming method according to the second embodiment of the present invention will be described with reference to FIG.

  The basic structure and the basic manufacturing method are the same as those in the first embodiment. Therefore, the description about the matter demonstrated in 1st Embodiment and the matter which can be easily guessed from 1st Embodiment is abbreviate | omitted.

  First, as shown in FIG. 3A, a silicon oxide film (lower insulating layer) 301 having a thickness of 4 nm or less is formed on a semiconductor substrate 300. After forming the silicon oxide film 301, nitrogen may be introduced by thermal nitridation or the like.

  Next, germanium hydride is introduced into a reaction vessel at a temperature of 500 ° C. or lower and a pressure of 10 to 100 Torr. In this case, germanium hydride is hardly decomposed, and a germanium hydride adsorption layer (germanium compound adsorption layer) 302 is adsorbed on the silicon oxide film 301 as a germanium-containing layer, as shown in FIG. At this time, in order to ensure the flatness of the adsorption layer 302, the thickness of the adsorption layer 302 is desirably one molecular layer or less.

  Then, heat treatment is performed at a high temperature of 700 ° C. to 900 ° C. to decompose germanium hydride in the adsorption layer 302. Thereby, germanium diffuses into the silicon oxide film 301 and the upper part of the silicon oxide film 301 reacts with germanium. As a result, as shown in FIG. 3C, a layer containing silicon, germanium and oxygen as an intermediate insulating layer (hereinafter referred to as a silicon germanium oxide layer for convenience) is formed in the upper layer region (upper part) of the silicon oxide film 301. 303) is formed.

  Thereafter, as shown in FIG. 3D, a silicon oxide film (upper insulating layer) 304 is formed by CVD. Although the CVD method is used here, an ALD method may be used. In this manner, a tunnel insulating film 305 having a silicon oxide film (lower insulating layer) 301, a silicon germanium oxide layer (intermediate insulating layer) 303, and a silicon oxide film (upper insulating layer) 304 is formed.

  According to the embodiment, germanium hydride is thinly adsorbed on the silicon oxide film 301, and heat treatment is performed after the adsorption. As a result, germanium diffuses into the silicon oxide film 301 and the upper portion of the silicon oxide film 301 is converted into a silicon germanium oxide layer 303 with high flatness. As a result, the tunnel insulating film 305 having excellent flatness is formed.

  As described above, also in this embodiment, a silicon germanium oxide layer is formed in the tunnel insulating film 305 as in the first embodiment. As a result, as in the first embodiment, the charge assist level caused by the silicon germanium oxide is formed in the tunnel insulating film 305, and the electron injection efficiency at the time of data writing is improved.

In this embodiment, germanium hydride (GeH ₄ ) is used as the source gas containing germanium. However, other gas species such as germanium tetrachloride (GeCl ₄ ) may be used.

(Third embodiment)
Next, a tunnel insulating film forming method according to the third embodiment of the present invention will be described with reference to FIG.

  The basic structure and the basic manufacturing method are the same as those in the first embodiment. Therefore, the description about the matter demonstrated in 1st Embodiment and the matter which can be easily guessed from 1st Embodiment is abbreviate | omitted.

  First, as shown in FIG. 4A, a silicon oxide film 401 is formed on a semiconductor substrate 400. After forming the silicon oxide film 401, nitrogen may be introduced by thermal nitridation or the like.

  Thereafter, as shown in FIG. 4B, a raw material gas containing silicon is introduced into the reaction vessel, and a thin silicon layer 402 having a thickness of 1 atomic layer or more and 1 nm or less is deposited. Note that the thickness of the silicon layer 402 may be one atomic layer or more in order to improve the flatness, but it is desirable to make it thicker than necessary in order to easily convert the entire silicon layer into a silicon oxide film. Absent. Typically, it is 1 atomic layer or more and 1 nm or less.

  Subsequently, a source gas containing germanium such as germanium hydride, or a source gas containing silicon and a source gas containing germanium are introduced into the reaction vessel. As a result, as shown in FIG. 4C, a germanium-containing film or a film containing silicon and germanium is deposited as the germanium-containing layer 403.

A desirable method for forming the silicon layer 402 and the germanium-containing layer 403 is as follows. First, silane (SiH ₄ ) gas is introduced into the reaction apparatus under conditions of a temperature of 400 to 550 ° C. and a pressure of several tens to 300 Torr. Thereafter, germanium hydride gas or a mixture of germanium hydride gas and silane gas is introduced into the reactor. Silane is used as the source gas containing silicon. However, for example, disilane (Si ₂ H ₆ ) gas may be used. Desirable film forming conditions when disilane gas is used are a temperature of 400 to 500 ° C. and a pressure of 100 to 300 Torr.

  Thereafter, as shown in FIG. 4D, a silicon oxide film 404 is formed by a CVD method using TEOS and ozone gas. At this time, first, the germanium-containing layer 403 is converted into a silicon germanium oxide layer 403a. That is, silicon and oxygen contained in TEOS and ozone gas react with the germanium-containing layer 403 to form the silicon germanium oxide layer 403a. Further, the silicon layer 402 is converted into a silicon oxide film or a silicon germanium oxide layer. Although the CVD method is used here, an ALD method may be used. Furthermore, a chemical sputtering method in an oxidizing atmosphere or a high temperature coating method of about 400 ° C. or higher may be used. In this manner, a tunnel insulating film 405 having a silicon oxide film (lower insulating layer) 401, a silicon germanium oxide layer (intermediate insulating layer) 403a, and a silicon oxide film (upper insulating layer) 404 is formed.

  Since there are few adsorption sites on the silicon oxide film and germanium-containing source gas such as germanium hydride has a low adsorption probability, nuclei are likely to be formed on the silicon oxide film, resulting in poor flatness. In the present embodiment, since the silicon layer 402 having more adsorption sites on the surface is formed first, it is possible to form the germanium-containing layer 403 with high flatness.

  Also in this embodiment, a silicon germanium oxide layer is formed in the tunnel insulating film 405 as in the first embodiment. As a result, as in the first embodiment, the charge assist level resulting from the silicon germanium oxide is formed in the tunnel insulating film 405, and the electron injection efficiency at the time of data writing is improved.

  Next, a tunnel insulating film forming method according to the fourth embodiment of the present invention will be described with reference to FIG.

  The basic structure and the basic manufacturing method are the same as those in the first embodiment. Therefore, the description about the matter demonstrated in 1st Embodiment and the matter which can be easily guessed from 1st Embodiment is abbreviate | omitted.

  First, as shown in FIG. 5A, a silicon oxide film 501 is formed on a semiconductor substrate 500. After forming the silicon oxide film 501, nitrogen may be introduced by thermal nitridation or the like.

  Thereafter, as shown in FIG. 5B, a source gas containing silicon is introduced into the reaction vessel, and a thin silicon layer 502 having a thickness of 1 atomic layer or more and 1 nm or less is deposited. Note that the thickness of the silicon layer 502 may be one atomic layer or more in order to improve the flatness, but it is desirable that the silicon layer 502 be thicker than necessary in order to easily convert the entire silicon layer into a silicon oxide film. Absent. Typically, it is 1 atomic layer or more and 1 nm or less.

  Subsequently, a source gas containing germanium such as germanium hydride, or a source gas containing silicon and a source gas containing germanium are introduced into the reaction vessel. As a result, as shown in FIG. 5C, a germanium-containing film or a film containing silicon and germanium 503 is deposited as the germanium-containing layer 503.

  A desirable method for forming the silicon layer 502 and the germanium-containing layer 503 is as follows. First, silane gas is introduced into the reactor under conditions of a temperature of 400 to 550 ° C. and a pressure of several tens to 300 Torr. Thereafter, germanium hydride gas or a mixture of germanium hydride gas and silane gas is introduced into the reactor. In addition, although silane was used as source gas containing silicon, for example, disilane gas may be used. Desirable film forming conditions when disilane gas is used are a temperature of 400 to 500 ° C. and a pressure of 100 to 300 Torr.

Thereafter, as shown in FIG. 5D, heat treatment is performed in an oxidizing atmosphere. As a result, germanium, oxygen (for example, oxygen in an oxidizing atmosphere) and silicon (for example, silicon in the silicon layer 502) in the germanium-containing layer 503 react to form a silicon germanium oxide layer 503a. Desirable oxidizing atmosphere conditions are, for example, a temperature of 650 to 1000 ° C. and a pressure of 400 to 760 Torr, and heat treatment is performed by introducing nitrogen (N ₂ ) gas and oxygen (O ₂ ) gas. Further, ozone, oxygen, water vapor, oxygen radical, oxygen ion, hydroxide ion, or hydrogen radical may be used as the oxidizing agent.

  Next, as shown in FIG. 5E, a silicon oxide film 504 is formed by a CVD method using TEOS and ozone gas. Although the CVD method is used here, an ALD method, a sputtering method, a coating method, or the like may be used. In this manner, a tunnel insulating film 505 having a silicon oxide film (lower insulating layer) 501, a silicon germanium oxide layer (intermediate insulating layer) 503 a and a silicon oxide film (upper insulating layer) 504 is formed.

  Since there are few adsorption sites on the silicon oxide film and germanium-containing source gas such as germanium hydride has a low adsorption probability, nuclei are likely to be formed on the silicon oxide film, resulting in poor flatness. In the present embodiment, since the silicon layer 502 having more adsorption sites on the surface is formed in advance, the germanium-containing layer 503 having high flatness can be formed as in the third embodiment. It is.

  Also in this embodiment, a silicon germanium oxide layer is formed in the tunnel insulating film 505 as in the first embodiment. As a result, as in the first embodiment, the charge assist level caused by the silicon germanium oxide is formed in the tunnel insulating film 505, and the electron injection efficiency at the time of data writing is improved.

  Next, a tunnel insulating film forming method according to the fifth embodiment of the present invention will be described with reference to FIG.

  The basic structure and the basic manufacturing method are the same as those in the first embodiment. Therefore, the description about the matter demonstrated in 1st Embodiment and the matter which can be easily guessed from 1st Embodiment is abbreviate | omitted.

  First, as shown in FIG. 6A, a silicon oxide film 601 having a thickness of 4 nm or less is formed on a semiconductor substrate 600. After forming the silicon oxide film 601, nitrogen may be introduced by thermal nitridation or the like.

  Next, germanium hydride is introduced into a reaction vessel at a temperature of 500 ° C. or lower and a pressure of 10 to 100 Torr. In this case, germanium hydride is hardly decomposed, and a germanium hydride adsorption layer (germanium compound adsorption layer) 602 is adsorbed on the silicon oxide film 601 as a germanium-containing layer, as shown in FIG. At this time, in order to ensure the flatness of the adsorption layer 602, the thickness of the adsorption layer 602 is desirably one molecular layer or less.

  Thereafter, heat treatment is performed at a high temperature of 700 ° C. to 900 ° C. to decompose germanium hydride in the adsorption layer 602. As a result, germanium diffuses into the silicon oxide film 601 and the silicon oxide film 601 and germanium react. As a result, a silicon germanium oxide layer 603 is formed in the upper layer region of the silicon oxide film 601 as shown in FIG.

  Thereafter, as shown in FIG. 6D, an additional silicon oxide film 604 is formed on the silicon germanium oxide layer 603 by using the CVD method. Although the CVD method is used here, an ALD method may be used.

  Next, germanium hydride is introduced into a reaction vessel at a temperature of 500 ° C. or lower and a pressure of 10 to 100 Torr. Thereby, as shown in FIG. 6E, a germanium hydride adsorption layer (germanium compound adsorption layer) 605 is formed on the silicon oxide film 604 as an additional germanium-containing layer. At this time, in order to ensure the flatness of the germanium layer 605, the thickness of the germanium layer 605 is desirably one molecular layer or less.

  Thereafter, heat treatment is performed at a high temperature of 700 ° C. to 900 ° C. to decompose germanium hydride in the adsorption layer 605. Thereby, germanium diffuses into the silicon oxide film 604, and the silicon oxide film 604 and germanium react. As a result, an additional silicon germanium oxide layer 606 is formed on the silicon germanium oxide layer 603 as shown in FIG.

  Thereafter, a silicon oxide film (not shown) is formed on the silicon germanium film 606 using a CVD method. Thereafter, the step of adsorbing the germanium hydride adsorption layer described with reference to FIG. 6E on the silicon oxide film, the step of performing the high heat treatment described with reference to FIG. The step of forming the oxide film may be repeated as many times as desired. Further, the thickness of the silicon oxide film formed can be appropriately changed by the CVD method.

  In this manner, a silicon oxide film (lower insulating layer) 601, a silicon germanium oxide layer (intermediate insulating layer) 603, one or more additional silicon germanium oxide layers (additional intermediate insulating layer) 606, and silicon oxide A tunnel insulating film having a film (upper insulating layer, not shown) is formed.

  According to the above embodiment, the steps of forming the germanium hydride adsorption layer on the silicon oxide film, forming the silicon germanium oxide layer by high-temperature heat treatment, and forming the silicon oxide film by the CVD method are two steps. Repeatedly, the tunnel insulating film is formed. By repeating the above three steps a plurality of times, a region where germanium is present in the tunnel insulating film becomes wider in the film thickness direction. As a result, the charge injection efficiency can be improved as described below.

  A case where a voltage is applied to the tunnel insulating film will be described with reference to FIGS. FIG. 7 is an energy band diagram, and FIG. 8 is a diagram showing the relationship between tunnel current and voltage.

  As shown in FIG. 7, charge assist levels 700 and 701 based on germanium exist in the tunnel insulating film.

  Further, in FIG. 8, a line A shows a case where the germanium distribution in the tunnel insulating film is wide, a line B shows a case where the germanium distribution is narrow, and a line C shows a case where no germanium is distributed.

  When a high voltage at the time of data writing operation is applied to the tunnel insulating film, an energy band state as shown in FIG. As a result, charges from the semiconductor substrate are injected into the floating gate electrode via the charge assist level 700.

  Further, since electrons are accumulated in the floating gate electrode during the data write operation, the effective voltage applied to the tunnel insulating film is reduced as compared with the start of write. However, as shown in FIG. 7B, when the region where germanium is present is wide in the film thickness direction, the electron tunnel is assisted even if the effective applied voltage is reduced, and the current density is increased as compared with the conventional case. be able to.

  On the other hand, when the region where germanium is present is narrow, the electron tunnel is not assisted as shown in FIG. For this reason, as shown by the line B in FIG. 8, when the applied voltage decreases, the current density does not increase.

  Thus, in this embodiment, the region where germanium is present can be widened in the film thickness direction. For this reason, as shown by the line A in FIG. 8, it is possible to increase the current density even at a low voltage, and the effect of improving the writing efficiency can be further expected.

  In this embodiment, germanium hydride is used as the source gas containing germanium. However, other gas species may be used, for example, germanium tetrachloride gas.

  In the first to fifth embodiments described above, the nonvolatile semiconductor memory device in which the floating gate electrode is provided between the tunnel insulating film and the interelectrode insulating film has been described. However, instead of the floating gate electrode, charge storage insulation is performed. The tunnel insulating film described in the first to fifth embodiments also applies to a charge trap type (MONOS type or the like) nonvolatile semiconductor memory device in which a film is provided and a charge block insulating film is provided instead of the interelectrode insulating film. Is applicable.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining the disclosed constituent elements. For example, even if several constituent requirements are deleted from the disclosed constituent requirements, the invention can be extracted as long as a predetermined effect can be obtained.

1 is a cross-sectional view schematically showing a configuration of a semiconductor device according to a first embodiment of the present invention. It is sectional drawing which showed typically a part of manufacturing process of the semiconductor device which concerns on the 1st Embodiment of this invention. It is sectional drawing which showed typically a part of manufacturing process of the semiconductor device which concerns on the 2nd Embodiment of this invention. It is sectional drawing which showed typically a part of manufacturing process of the semiconductor device which concerns on the 3rd Embodiment of this invention. It is sectional drawing which showed typically a part of manufacturing process of the semiconductor device which concerns on the 4th Embodiment of this invention. It is sectional drawing which showed typically a part of manufacturing process of the semiconductor device which concerns on the 5th Embodiment of this invention. It is an energy band figure of the semiconductor device which concerns on the 5th Embodiment of this invention. FIG. 10 is a diagram illustrating a relationship between a tunnel current and a voltage according to a fifth embodiment of the present invention.

Explanation of symbols

100, 200, 300, 400, 500, 600 ... Semiconductor substrate 103, 204, 305, 405, 505 ... Tunnel insulating film 104 ... Floating gate electrode 105 ... Interelectrode insulating film 106 ... Control gate electrode 201, 203, 301, 304 401, 404, 501, 504, 601, 604 ... Silicon oxide film 202, 302, 403, 503, 602, 605 ... Germanium-containing layer 202a, 303, 403a, 503a, 603, 606 ... Silicon germanium oxide layer 402, 502 ... Silicon layer

Claims (5)

A first insulating film formed on a semiconductor substrate; a charge storage layer formed on the first insulating film; a second insulating film formed on the charge storage layer; A method of manufacturing a semiconductor device comprising a control gate electrode formed on an insulating film,
The step of forming the first insulating film includes:
Forming a lower insulating layer containing silicon and oxygen as main components;
Forming a germanium-containing layer containing germanium as a main component on the lower insulating layer;
A step of forming an intermediate insulating layer containing silicon, germanium, and oxygen as main components by a reaction of the germanium-containing layer, silicon, and oxygen;
Forming an upper insulating layer containing silicon and oxygen as main components on the intermediate insulating layer;
A method for manufacturing a semiconductor device, comprising: The reaction of the germanium-containing layer, silicon and oxygen is
The method of manufacturing a semiconductor device according to claim 1, comprising a reaction between a gas containing silicon and oxygen and the germanium-containing layer. The reaction of the germanium-containing layer, silicon and oxygen is
The method for manufacturing a semiconductor device according to claim 1, comprising a reaction between an upper portion of the lower insulating layer and the germanium-containing layer. Forming an additional oxide layer containing silicon and oxygen as main components on the intermediate insulating layer;
Forming an additional germanium-containing layer containing germanium as a main component on the additional oxide layer;
Reacting the additional oxide layer with the additional germanium-containing layer to form an additional intermediate insulating layer containing silicon, germanium and oxygen as main components;
The method of manufacturing a semiconductor device according to claim 3, further comprising: A first insulating film formed on a semiconductor substrate; a charge storage layer formed on the first insulating film; a second insulating film formed on the charge storage layer; A control gate electrode formed on the insulating film, and a semiconductor device comprising:
The first insulating film includes a lower insulating layer containing silicon and oxygen as main components, an intermediate insulating layer formed on the lower insulating layer and containing silicon, germanium, and oxygen as main components, and the intermediate insulating material. A semiconductor device comprising: an upper insulating layer formed over the layer and containing silicon and oxygen as main components.

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