JPH03268445A - Manufacture of semiconductor substrate for semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To substantially eliminate any defect in a semiconductor device formation region even in the vicinity of a groove by forming the lower surface of a third film into less thickness of the same such that the same is located higher than the lower surface of a first film. CONSTITUTION:A third film 13, a Si oxide connected to a first film 21 is formed on the upper surface of a buried material part 12 into less thickness than the first film 21 such that the lower surface thereof is located higher than the lower surface of the first film 21. Accordingly, even if opposite ends of the first film 21 viewed in a cross section perpendicular to the length thereof are formed to be a bird's beak, the first and third films 21, 13 may be formed to thicknesses corresponding to the thickness of the film 13 or less, so that they can be formed thinner. Further, since there is existent the first film 21 when the third film 13 is formed, a bird's leg is substantially prevented from being formed extending from the third film 13. Hereby, any defect in a semiconductor device formation region is substantially prevented from being produced in the vicinity of a groove.

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD 1 The present invention relates to a method for manufacturing a semiconductor substrate for a semiconductor integrated circuit in which semiconductor element formation regions are separated from each other by a substrate. [Prior Art] Conventionally, a method for manufacturing a semiconductor substrate for a semiconductor integrated circuit has been proposed as described below with reference to FIG. That is, a semiconductor substrate 1 made of Si and having a flat main surface 1a is prepared in advance (FIG. 2A), and a relatively thin layer is formed on the main surface 1a of the semiconductor substrate 1 by thermal oxidation. A film 2 made of S oxide is formed, then a film 113 made of Si nitride is formed on vA2 by CVD method, and then a film 4 made of glass (PSG) material is formed on wA3. By this, main surface 1 of semiconductor substrate 1
A mask material layer 5 is formed in which the layers 2, 3 and 4 are laminated in this order (FIG. 2B). Next, the mask material layer 5 is subjected to a reactive ion etching process using a corresponding mask (not shown) to define semiconductor element formation regions that separate the semiconductor substrate 1 from each other. In the area above the area where the full 10 is formed, W7A6 is formed which has a pattern corresponding to the pattern of the full 10 and exposes the area of the semiconductor substrate 1 where the full 10 is formed (FIG. 2C). . Next, by performing a reactive ion etching process on the semiconductor substrate 1 using the mask material JI5 forming the window 6 as a mask, the semiconductor substrate 1 is etched in the region of the mask material layer 5 facing the window 6. Grooves 10 are formed in semiconductor element formation regions 8 and 9 separated by H (FIG. 2D). Next, the film 4, which is the uppermost part of the mask material layer 5, is removed by wet etching,
Therefore, from the mask material layer 5, the g! A masking material layer 5' is formed which does not have 4 but does have films 2 and 3 and has a window 6' corresponding to the window 6 described above (FIG. 2E). Next, a relatively thin film 11 made of SiM compound is formed on the inner surface of the semiconductor substrate 1 by thermal oxidation with the main surface 1a of the semiconductor substrate 1 being used as a mask by the mask material layer 5'. form (Fig. 2 [). Next, a embedding material layer 12 made of polycrystalline Si or amorphous S is placed on the main surface 1a of the semiconductor substrate 1 via a mask material layer 5'.
is formed to a relatively thick thickness, about the width of the groove 10, so that the groove 10 is completely filled through the groove 11 and the window 6' is also completely filled (FIG. 2G). Next, by reactive ion etching treatment of the embedded UP) 12 from above, the embedded material layer 12 is etched in the area where the upper surface is in the vicinity of 'g6' or in the vicinity of the window 6. The masking material layer 12' is left at a height of 5', but a portion of the embedding material layer 12 above the mask material layer 5' is removed so that it does not remain (Fig. 2, 11). ). Next, a thermal oxidation method is applied with the main surface 1a of the semiconductor substrate 1 being masked by the masking material layer 5', and a masking material layer 5' made of SiM compound is formed on the upper surface of the buried material portion 12'.
The film 13 that is connected to the film 11 formed on the inner surface of the groove 10 and the groove 10 constituting the mask material MI5' is arranged so that the free end on the window 6' side of 813 that makes up the mask material MI5' is upward. The mask material layer 5' is formed so thick that it can be extruded (FIG. 2, 1). Next, the mask material layer 5' is removed from the main surface 1a of the semiconductor substrate 1 (FIG. 2, J). At this time, the upper surface of 1113 is removed by the thickness of crotch 2 of mask material layer 5'. The above is a conventionally proposed method for manufacturing a semiconductor substrate for a semiconductor integrated circuit. A semiconductor substrate for a semiconductor integrated circuit (FIG. 2 J) manufactured by such a method for manufacturing a semiconductor substrate for a semiconductor integrated circuit has semiconductor element forming regions 8 and 9 separated into H by a groove ]O. Right configuration and SiM
A film 13 made of SiM is formed between the semiconductor element forming regions 8 and 9 of the semiconductor substrate 1 by forming a groove 10 that defines them.
The tray 10 is bridged and extended while being supported by a filling material 12 made of polycrystalline Si or amorphous Si buried through a film 11 made of a compound. For this reason, a semiconductor substrate for a semiconductor integrated circuit (J in FIG. 2) manufactured by the conventional method for manufacturing a semiconductor substrate for a semiconductor integrated circuit shown in FIG. The semiconductor elements formed or to be formed in the formation regions wL8 and 9 are connected to n by extending the wiring layer on the film 13 made of Si oxide that extends horizontally over the area wL8 and 9. It has a function that allows you to The conventional method for manufacturing a semiconductor substrate for a semiconductor integrated circuit shown in FIG.
A step of forming a mask material layer 5 (FIG. 2B) and a step of forming a window 6 in the mask material layer 5 in a region above the region where the post-M layer 10 of the semiconductor substrate 1 is formed (second step). Figure C)
, a step (D) of forming a tray 10 on the semiconductor substrate 1 in a region facing the window 6 of the mask material layer 5 (FIG. 2D);
Step of forming a film 11 made of SiM compound on the inner surface of 10 (
Figure 2 F), within 10 minutes, through the discipline 11,
a step of embedding a embedding material portion 12' made of amorphous Si or amorphous Si (FIG. 2H), and a step of forming a film 13 of S1 oxide on the upper surface of the embedding material portion 12' It can be manufactured relatively easily by a relatively simple method having FIG. 1). In this case, in the process of forming the film 13 (FIG. 2 1), as shown in FIG. Since the film 13 can be easily formed in the shape of It can be formed without creating a sharp step. Therefore, according to the conventional manufacturing method of a semiconductor substrate for a semiconductor integrated circuit shown in FIG. It can be easily manufactured as there is no risk of causing disconnection in the wiring layer extended on the film 13 for this purpose. [Problems to be Solved by the Invention] However, in the conventional manufacturing method of a semiconductor substrate for a semiconductor integrated circuit as described above in FIG. As described above, the membrane 13 which extends through the groove 10 can be formed into a bird's beak shape on both sides when viewed in a cross section perpendicular to the length direction. Parts 13c and 13d extending downward from the film 13 in a bird's leg shape along the opposing inner surfaces of the 10 are formed into semiconductor element forming regions 8 and 9 from the opposing inner surfaces of the 10.
It is formed while applying stress to the sides. For this reason, the semiconductor element formation regions 14!8 and 9 are approximately 10.
It is obtained by defining that the stress is received at a relatively large value in the vicinity of It has the disadvantage that it can be obtained by defining it as a covering. Therefore, it is an object of the present invention to propose a method for manufacturing a semiconductor substrate for a semiconductor integrated circuit according to the Ili standard without the above-mentioned drawbacks. Means for Solving Problems] The method for manufacturing a semiconductor substrate for a semiconductor integrated circuit according to the present invention is as follows:
In the main surface of a semiconductor substrate made of Si, in a region where a groove is formed that separates the semiconductor substrate into h sections and defines a semiconductor element formation region, a cross section that covers the region and is perpendicular to the length direction. a step of locally forming a first film made of a 5iFIlf compound having a relatively thick P thickness with bird's beak shapes on both sides when viewed; and (2) forming the groove of the semiconductor substrate in the first film; (1) forming a groove in the half U-plate in the area facing the window; (2) forming a SiM compound on the inner surface of the groove; A step of forming a second discipline consisting of;
(2) burying an embedding material made of polycrystalline Si or amorphous S1 in the groove through the second film so that its upper surface is located at a height within the window; , (2) A third film made of SiM compound connected to the first film is placed on the top surface of the embedding material part so that the bottom surface is located at a higher position than the bottom surface of the first film; forming the first film to have a smaller thickness than the first film.

[Action/effect]

The semiconductor substrate for a semiconductor integrated circuit manufactured by the method for manufacturing a semiconductor substrate for a semiconductor integrated circuit according to the present invention is the same as the semiconductor substrate for a semiconductor integrated circuit manufactured by the conventional method for manufacturing a semiconductor substrate for a semiconductor integrated circuit described above in FIG. In the same manner as in the case of FIG. Corresponding to the film in the case of a semiconductor substrate for a semiconductor integrated circuit by the above-mentioned conventional manufacturing method of a semiconductor substrate for a semiconductor integrated circuit, these are defined in the gate of the semiconductor element formation region defined by the groove of the semiconductor substrate. A groove is formed on the inner surface of the S
The groove is extended horizontally in a state where it is supported by a filling material part made of polycrystalline Si or amorphous Si filled through a film made of an il compound. Therefore, the semiconductor substrate for semiconductor integrated circuits manufactured by the method for manufacturing a semiconductor substrate for semiconductor integrated circuits according to the present invention is also suitable for semiconductor integrated circuits manufactured by the conventional method for manufacturing semiconductor substrates for semiconductor integrated circuits as described above in FIG. As in the case of a semiconductor substrate, the semiconductor elements formed or to be formed in the semiconductor element forming regions, which are divided into 1111 parts by grooves, are extended horizontally across the 1111 parts.
It has a function of being able to connect by extending the wiring layer over the vA made of the first and third films made of M oxide. The method for manufacturing a semiconductor substrate for a semiconductor integrated circuit according to the present invention is to produce a semiconductor substrate for a semiconductor integrated circuit having the above-mentioned functions by performing the steps specified in the column of [Means for Solving the Problems 1]. Similar to the conventional manufacturing method of semiconductor substrates for semiconductor integrated circuits as described above in Figure 2, it is a relatively simple method and relatively easy! In can be done. Further, in this case, in the step of forming the first film, the first film can be easily formed so that both sides thereof have a bird's beak shape when viewed in a cross section perpendicular to the length direction, and In the step of forming the third film, the third film can be easily formed so that its top surface is at approximately the same height as the top surface of the film, so that To easily form a film without creating a sharp step between itself and a semiconductor element formation region defined by a groove on the main surface of a semiconductor substrate. be able to. Therefore, in the method for manufacturing a semiconductor substrate for a semiconductor integrated circuit according to the present invention, the grooves of the semiconductor substrate for a semiconductor integrated circuit are The arrangement 1Wj can be easily manufactured without the possibility of disconnection in order to connect the semiconductor elements formed or to be formed in the semiconductor element formation regions defined by the . However, in the method of manufacturing a semiconductor substrate for a semiconductor integrated circuit according to the present invention, in the step of forming the first film, both ends of the first film when viewed in a cross section perpendicular to the length direction are shaped like a bird's beak. Even if the first and third films are formed to have a thickness corresponding to or less than the thickness of the film 13 formed by the conventional manufacturing method of a semiconductor substrate for semiconductor integrated circuits as described above in FIG. In addition, in the step of forming the third film, the third film can also be formed thinly for the reasons mentioned above, and the third film can be formed thinly. When forming and covering, since the first film is present, the bird's leg part as described above in the case of the conventional manufacturing method of a semiconductor substrate for semiconductor integrated circuit shown in FIG. 2 is formed extending from the third film. There is virtually no such thing. For this reason, the semiconductor element forming region defined by the groove hardly receives stress even in the vicinity of the groove, or even if it does receive stress, as described above in FIG. The semiconductor element formation area defined by the grooves is free from defects, which are obtained by defining the semiconductor element forming area as being significantly smaller than in the case of the manufacturing method of semiconductor substrates for semiconductor integrated circuits. Even in the vicinity of the groove, there is hardly any, or even if there is, it is far negligible compared to the case of the conventional manufacturing method of a semiconductor substrate for semiconductor integrated circuits as described above in FIG. It is obtained by defining it as [Embodiment] Next, an embodiment of the method for manufacturing a semiconductor substrate for a semiconductor integrated circuit according to the present invention will be described with reference to FIGS. 1A to 1K. In FIG. 1, parts corresponding to those in FIG. 2 are designated by the same reference numerals. The embodiment of the method for manufacturing a semiconductor substrate for a semiconductor integrated circuit according to the present invention shown in FIGS. A semiconductor substrate for a semiconductor integrated circuit is manufactured. That is, as in the case of the conventional manufacturing method of a semiconductor substrate for a semiconductor integrated circuit described above with reference to FIG. 2, a semiconductor substrate 1 made of Si and having a flat main surface 1a is prepared in advance. Then, the semiconductor substrate 1 is placed on the main surface 1a of the semiconductor substrate 1.
In a region where a groove 10, which will be described later, is formed between semiconductor element forming regions 8 and 9 that separate the semiconductor element formation regions 8 and 9 from each other,
A film 21 made of Si oxide, which covers the area and has a relatively thick bird's beak shape on both sides 21a and 21b when viewed in a cross section perpendicular to the length direction, is formed by a thermal oxidation method known per se. Locally formed (Fig. 1B)
. Next, on the main surface 1a of the semiconductor substrate 1, on the area where the film 21 is not formed and on the WA 21, according to the conventional method for manufacturing semiconductor gJ and integrated circuit semiconductor substrates described above in FIG. By thermal oxidation, the film 2 made of a silicide is continuously extended on the area where the film 21 is not formed on the main surface 1a of the semiconductor substrate 1 and on the film 21. In this case,
Membrane 2 is g! 2i, the film 21 of the semiconductor substrate 1
Although it is formed to a sufficiently thinner thickness than the region where it is not formed, the figure shows a case where it is formed to the same thickness for the sake of simplicity. ), Next, a layer 3 made of Si nitride is formed on the film 2 by the CVD method, as in the case of the conventional manufacturing method of a semiconductor substrate for a semiconductor integrated circuit described above in FIG. On the m3, an F! made of glass (PSG) material is placed, as in the case of the conventional manufacturing method of semiconductor substrates for semiconductor integrated circuits as described above in FIG. 4 on the main surface 1a of the semiconductor substrate 1. 21 is not formed and on the film 21, those II! 2. Mask material rjA5 in which 3 and 4 are sequentially laminated in that order
are formed by continuously extending them (Fig. 1C). Next, the mask material layer 5 is subjected to a reactive ion etching process using a mask (not shown) for the semiconductor substrate, in accordance with the conventional manufacturing method of semiconductor substrates for semiconductor integrated circuits as described above in FIG. In a region above a region in which a groove 10 described below is formed, which is defined in a semiconductor element forming region separating the substrate 1 from each other, a groove 10 having a pattern corresponding to the pattern 110 and a groove of the semiconductor substrate 1 is formed. 10 is formed in cooperation with the window 26 described below to form a window 6 for facing all outside, and then the film 21 is connected to the window 6 of the mask material layer 5 just formed. (FIG. 1D). Next, the semiconductor substrate 1 is subjected to a reactive ion etching process using the mask material layer 5 forming the window 6 as a mask, in accordance with the conventional manufacturing method of a semiconductor substrate for a semiconductor integrated circuit as described above with reference to FIG. As a result, semiconductor element forming regions 8 and 9 are defined in the semiconductor substrate 1, which are separated from each other in the region facing the window 6 of the mask material layer 5 and the window 26 of the film 21. Form a groove 10 (
Figure 1E). Next, as in the case of the conventional manufacturing method of a semiconductor substrate for a semiconductor integrated circuit described above in FIG. 2, the uppermost film 14 constituting the mask material layer 5 is removed by wet etching treatment. Therefore, from the mask material layer 5, the film 4 does not have 112 and 3 and the above-mentioned window 6
Form a mask material layer 5' having a window 6' corresponding to (
Figure 1 F). Next, in accordance with the conventional manufacturing method of a semiconductor substrate for a semiconductor integrated circuit as described above in FIG. A relatively thin film 11 made of Si oxide and connected to the film 21 is formed on the inner surface of the semiconductor substrate 1 (FIG. 1G). Next, polycrystalline Si or amorphous silicon is deposited on the main surface 1a of the semiconductor substrate 1 via a mask material layer 5' in accordance with the conventional method for manufacturing a semiconductor substrate for semiconductor integrated circuits as described above in FIG. A potting material 1!12 made of high quality Si is placed in the groove 1 so that the grooves 10 and 16' are completely interposed via the membrane 11.
It is formed to a relatively thick thickness with a width of 0 (Fig. 1 1-1).
) Next, in accordance with the conventional manufacturing method of a semiconductor substrate for a semiconductor integrated circuit described above in FIG.
By reactive ion etching treatment from above,
The embedding material layer 12 remains as the embedding material layer 12' whose upper surface is located at the height position within the window 6', but the part within the embedding material layer 12 remains at the height position within the window 6'. A portion of the mask material layer 5' is removed so that no portion remains (FIG. 1I). Next, using a thermal oxidation method with the main surface 1a of the semiconductor substrate 1 and the film 21 being masked by the mask material layer 5', a mask material layer made of SiM compound and a mask material layer is formed on the upper surface of the embedded material portion 12'. #! formed on the inner surface of the film 2 and the groove 10 that make up the groove 5'. The membrane 13 connected to A11 is formed to have a smaller thickness than the membrane 21 so that its lower surface is located at a position lower than the lower surface of the membrane 21 (FIG. 1J). In addition, in the figure, g! While the lower surface of WA 13 is located at a higher position than the lower surface of film 21, the upper surface of WA 13 is just above I of mask material layer 5'.
A case is shown where it is formed at the same height as the top surface of FJ2. Next, the mask material layer 5' is removed from the main surface 1a of the semiconductor substrate 1 and the film 21 in accordance with the conventional manufacturing method of a semiconductor substrate for a semiconductor integrated circuit described above with reference to FIG. J
). The above is an embodiment of the method for manufacturing a semiconductor substrate for a semiconductor integrated circuit according to the present invention. The semiconductor substrate for a semiconductor integrated circuit manufactured by the method for manufacturing a semiconductor substrate for a semiconductor integrated circuit according to the present invention is the same as the semiconductor substrate for a semiconductor integrated circuit manufactured by the conventional method for manufacturing a semiconductor substrate for a semiconductor integrated circuit described above in FIG. As in the case of a semiconductor substrate, it has a structure in which semiconductor element forming regions 8 and 9 are separated from each other by a width of 10 mm,
And F! made of SiM compound! A film 23 consisting of a film 13 and a film 21 is defined by the groove 10 of the semiconductor substrate 1 corresponding to the film 13 in the case of a semiconductor substrate for a semiconductor integrated circuit according to the conventional manufacturing method of a semiconductor substrate for a semiconductor integrated circuit as described above in FIG. Polycrystalline Si or amorphous silicon fills the area between the semiconductor element forming regions 8 and 9 formed through a layer of Si oxide formed on the inner surface thereof. It is supported by an embedded material part 12' made of Si, and is extended by bridging the part 10. Therefore, the semiconductor substrate for semiconductor integrated circuits (K in FIG. 1) manufactured by the semiconductor substrate for semiconductor integrated circuits according to the present invention shown in FIG. As in the case of semiconductor substrates for semiconductor integrated circuits manufactured by the manufacturing method of substrates,
Semiconductor element forming regions 8 separated from each other by
The semiconductor elements formed in and 9 and 16 can be interconnected by extending a wiring layer on the crotch 23 made of Si oxide which is extended by bridging W410. have The method for manufacturing a semiconductor board for a semiconductor integrated circuit according to the present invention shown in FIG.
In a, in the region where the groove 10 defined in the semiconductor element forming regions 8 and 9 separating the semiconductor substrate 1 from each other is formed, both sides as seen in a cross section that covers the region and intersects the longitudinal direction. A process of locally forming and covering a film 21 made of Si oxide having a relatively thick thickness in which portions 21a and 21b are shaped like bird's beaks (FIG. 1B), and forming grooves 10 of the semiconductor substrate 1 in the film 21. Window 2 that allows the area to be formed to be exposed to the outside
6 (FIG. 1D), and a step of forming a full 10 on the semiconductor substrate 1 in the area facing the window 6 (FIG. 1 E), the inner surface of the full 10 is made of Si oxide. In the process of forming the film 11 (FIG. 1G), Fi! 11, an embedded material part 12 made of polycrystalline S or amorphous Si
' in such a way that its upper surface is located at a height position within the window 6 (FIG. 1 1), and on the upper surface of the embedded material part 12',
A film 13 made of Si oxide and connected to the films 21 and 11
1121 to have a smaller thickness than 1121 so that the lower surface is located at a higher position than the lower surface of the membrane 21 (FIG. 1 J
) can be manufactured relatively easily by a relatively simple method similar to the method for manufacturing the conventional semiconductor substrate for semiconductor integrated circuits described above with reference to FIG. In addition, in this case, in the step of forming the film 21 (FIG. 1B), the film 21 can be easily formed so that both sides of the film 21 have a bird's beak shape when viewed in a cross section perpendicular to the length direction. In addition, in the step of forming the film 13 (FIG. 1J), the IIj 413 can be formed so that its upper surface is at approximately the same height as the upper surface of the film 21, and therefore The film 23 is applied to itself and the semiconductor (semiconductor element forming region 8 on the main surface 1a of the A male plate 1).
It is possible to form a sharp step between and 9 without crushing the cow. Therefore, in the case of the manufacturing method of the semiconductor substrate for semiconductor integrated circuits according to the present invention shown in FIG. The substrate is placed in its semiconductor element formation region 8.
and 9, and can be easily manufactured without the risk of causing disconnection in the wiring layer due to the connection of the semiconductor elements formed or to be formed. However, in the case of the method for manufacturing a semiconductor substrate for a semiconductor integrated circuit according to the present invention shown in FIG. 1, in the step of forming the film 21 (FIG. 1B), the film 21 is Even if both ends 21a and 21b are formed to have a bird's beak shape, the thickness of the films 21 and 13 corresponds to the thickness of the film 13 formed by the conventional manufacturing method of a semiconductor substrate for a semiconductor integrated circuit as described above in FIG. The film 13 can be formed thinly, and in the step of forming the film 13 (FIG. 1J),
The film 13 (a) can also be formed thinly by the extrusion described above, and the film (l!) can also be formed thinly by the extrusion process described above. 13, since the crotch 21 is present, the bird's leg portion 1 as described above in the case of the conventional manufacturing method of a semiconductor substrate for semiconductor integrated circuits as described above in FIG.
3c and 13d are substantially not formed extending from the film 13. For this reason, the semiconductor element formation regions [8 and 9 defined by the grooves 10 and 10] are capable of applying stress even in the vicinity of the grooves 10.
Either there is no ``reception number'', or even if there is, it is only received at a much smaller value than in the case of the conventional manufacturing method of semiconductor substrates for semiconductor integrated circuits as described above in Figure 2. Therefore, the semiconductor device forming regions 8 and 9 defined by the iM 10 are free from defects.
Even in the vicinity of the groove 10, there is hardly any, or even if there is, the amount is far negligible compared to the case of the conventional manufacturing method of a conductive substrate not used for semiconductor integrated circuits as described above in FIG. It is obtained by defining it as something that does not. The above description merely shows one embodiment of the method for manufacturing a semiconductor substrate for a semiconductor integrated circuit according to the present invention, and various modifications and changes may be made without departing from the spirit of the present invention. .

[Brief explanation of drawings]

FIGS. 1A to 1A are cross-sectional views showing sequential steps in an embodiment of the method for manufacturing a semiconductor substrate for a semiconductor integrated circuit according to the present invention. FIGS. 2A to 2J are line sectional views showing sequential steps in a conventional manufacturing method of a semiconductor substrate for a semiconductor integrated circuit. 1... Semiconductor substrate 1a...
...Main surface 2.3.4...Membrane 5.5'...Mask material layer 6.6'...Window 8.9... ......Semiconductor element formation region 10...
・・・・・・・・・・・・Man 11.13・・・・・・
Film 12 made of Si oxide...
・Embedded material layer 21... Film made of Si oxide 26... Window applicant Nippon Telegraph and Telephone Co., Ltd. Figure 1 Figure 2 Figure 2 Figure 2

Claims (1)

[Claims] Claim 1: In the main surface of a semiconductor substrate made of Si, in a region where a groove is formed that separates the semiconductor substrate from each other and defines a semiconductor element formation region, a groove that covers the region and extends in the longitudinal direction. a step of locally forming a first film made of Si oxide having a relatively thick thickness and having bird's beak shapes on both sides when viewed in a cross section perpendicular to the semiconductor substrate; forming a window that exposes a region where the groove is formed to the outside; forming the groove in the semiconductor substrate in a region facing the window; and forming an inner surface of the groove with Si oxide. a step of forming a second film; placing an embedded material part made of polycrystalline Si or amorphous Si in the groove through the second film, the top surface of which is at a height within the window; a step of embedding a third film made of Si oxide that is connected to the first and second films on the upper surface of the embedding material part, and a third film made of Si oxide that is connected to the first film and the bottom surface of the embedding material part is located on the first film; 1. A method for manufacturing a semiconductor substrate for a semiconductor integrated circuit, comprising the step of forming a first film thinner than a first film so as to be located at a higher position than a lower surface of the first film.