JPH08339972A - Manufacture of thin film transistor and liquid crystal display using it - Google Patents

Abstract

PURPOSE: To prevent the surface roughing of an active layer during laser irradiation and degradation in crystal quality associated therewith, by forming on a semiconductor in contact with a gate insulating film, another semiconductor the coefficient of laser light absorption of which is lower than that of the semiconductor, and the melting point of which is higher than that of the semiconductor, and irradiating it with laser. CONSTITUTION: ACr gate electrode 2, a silicon nitride film 3 as a gate insulating film, an amorphous silicon film 7 to be an active layer, and a microcrystalline silicon film 5 are continuously deposited on a glass substrate 1. Excimer laser of XeCl is applied in vacuum, and the amorphous silicon film is thereby crystallized to form a polycrystalline silicon film 6. Here, laser is absorbed only 10% or so if the thickness of the microcrystalline silicon film 5 is adjusted so that its coefficient of laser light absorption is lower than that of the amorphous silicon. Further, since the melting point of the microcrystalline silicon film is higher than that of the amorphous silicon film, the shape of the microcrystalline silicon film does not change, and the surface roughing of the polycrystalline silicon 6 is reduced. As a result it is possible to prevent degradation in crystal quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film semiconductor device,
In particular, it relates to a method and structure for manufacturing a thin film transistor for driving a liquid crystal display.

[0002]

2. Description of the Related Art Generally, a laser irradiation method for polycrystallizing an active layer of an inverted stagger type thin film transistor is described in a literature ("
73 (7), 3271 (1993) ") or by directly irradiating the active layer with a laser, or as described in JP-A-60-245124. Further, the active layer is irradiated through a transparent insulating film such as SiO ₂ on the active layer.

[0003]

In a conventional inverted staggered thin film transistor, an amorphous semiconductor is irradiated with a laser in order to polycrystallize an active layer for the purpose of increasing the operation speed. When the active layer is directly irradiated with laser, the surface of the film becomes rough due to bumping of hydrogen in the film, rapid heating, or rapid cooling, and the crystal quality also deteriorates. To prevent this, if the substrate is heated and dehydrogenated before laser irradiation, there is a problem that the characteristics of the amorphous thin film transistor that is not irradiated with laser used as a driving element of a pixel of a liquid crystal display deteriorates. Further, when the active layer is irradiated with a laser through the transparent insulating film, it is necessary to use a thin active layer for sufficient crystallization. In this case, in order to form the source and drain electrodes, it is necessary to establish a technique for selectively etching the ohmic contact layer on the active layer.

An object of the present invention is to provide a method of manufacturing a polycrystalline thin film transistor having high characteristics, which prevents surface roughness of an active layer and its accompanying deterioration of crystal quality during laser irradiation.

[0005]

A feature of the present invention for solving the above-mentioned problems is that a semiconductor is stacked on a semiconductor in contact with a gate insulating film and has a smaller light absorption coefficient for the laser and a higher melting point. Is to irradiate.

[0006]

According to the above-mentioned means, the energy during laser irradiation is hardly absorbed by the semiconductor having a small absorption coefficient in the upper layer, but is absorbed by the semiconductor in the lower layer and the lower layer is heated and melted.
Since the upper layer does not melt, when the lower layer solidifies, its shape reflects that of the upper layer, and it becomes possible to prevent surface roughness.

[0007]

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

FIG. 1 is a sectional view showing a manufacturing process of a thin film transistor in one embodiment of the present invention. First, as shown in (a), Cr is deposited on the glass substrate 1 by a 1200Å sputtering method and patterned to form the gate electrode 2. Then, the source gas SiH ₄ , NH ₃ , and N ₂ are respectively used in the plasma CVD method, and the silicon nitride film 3, SiH ₄ , and H ₂ which is a gate insulating film of 3500 Å are used, respectively.
Amorphous silicon film 4 which becomes an active layer of 0 to 600 Å, and 20 to 100 under the condition of large dilution of H ₂ using SiH ₄ and H ₂ as well.
The Å microcrystalline silicon film 5 is continuously deposited. Next, 220 mJ / cm ² of XeCl excimer laser is irradiated in vacuum to crystallize the amorphous silicon film 4 to form a polycrystalline silicon film 6. At this time, if the thickness of the microcrystalline silicon film 5 is 100 Å and the light absorption coefficient for the laser is about 1 × 10 ⁵ cm ^−1, which is smaller than 1 × 10 ⁶ cm ^{−1 of} amorphous silicon, the laser is Since it absorbs only about 10% and its melting point is higher than that of the amorphous silicon film 4, its shape does not change and the surface roughness of the polycrystalline silicon 6 is reduced. Then, the natural oxide film on the surface of the microcrystalline silicon film 5 is removed with a hydrofluoric acid-based aqueous solution, and then SiH ₄ and H ₂ are used to remove the impurities in the range 1600 to 2000
Of the amorphous silicon film 7, S which will become the etching stopper layer of
After continuously depositing n-type amorphous silicon 8 using iH ₄ , H ₂ and PH ₃ , chromium silicide (CrS
i) Form 9. Then, the films 3 to 9 are patterned into islands. Then, 2 by sputtering method
800Å ITO (Indium Tin Oxide) 10 is deposited. Next, as shown in (b), a resist 11 is applied and then formed into a predetermined shape for forming source and drain electrodes by photolithography. Then, as shown in (c), the ITO 10 is removed by wet etching with bromic acid to form source and drain electrodes 12 and 13. Then, the n-type amorphous silicon 8 is removed by the dry etching method using BCl ₃ to form the ohmic contact layer 14 to complete the thin film transistor.

According to the embodiment, since the amorphous silicon film 4 is covered with the microcrystalline silicon film 5 having a smaller light absorption coefficient for the laser and a larger melting point during the laser irradiation, the polycrystalline silicon 6 is formed. It is possible to prevent the surface quality from being deteriorated and the crystal quality from being deteriorated due to the surface roughness. And FIG.
As shown by the gate voltage-drain current characteristics, it is possible to manufacture a high-performance transistor having a high on-current and a low off-current as compared with a conventional polycrystalline thin film transistor manufactured by directly irradiating amorphous silicon with a laser. Further, since the surface roughness is eliminated, the contact characteristics between the microcrystalline silicon film 5 and the amorphous silicon film 7 are improved, the resistance thereof is decreased, and the on-current is further improved.

The active layer polycrystallized by laser irradiation is not particularly limited to amorphous silicon, and any kind of semiconductor may be selected as long as it is a semiconductor which is crystallized by laser irradiation and has high conductivity. For example, 2 amorphous germanium
When laser is irradiated after depositing 00-600Å and depositing microcrystalline silicon in the same manner as in the above-described embodiment, amorphous germanium has a larger light absorption coefficient for laser than amorphous silicon and has a lower melting point. Energy can be reduced, and a transistor can be manufactured at a lower process temperature. Further, the film that covers the lower layer semiconductor at the time of laser irradiation is not limited to microcrystalline silicon, and if the semiconductor film is smaller than the lower layer semiconductor in terms of light absorption coefficient, high melting point, and high conductivity, the type of the film is particularly limited. Not selected. For example, in the case of microcrystalline silicon carbide (SiC),
Since the melting point is higher than that of amorphous silicon and the light absorption coefficient is lower than that of microcrystalline silicon, amorphous silicon can be crystallized with lower laser energy, and damage to the active layer by laser can be reduced. The etching stopper layer is not limited to amorphous silicon as long as it is a semiconductor film having high conductivity. For example, if the etching stopper layer is an amorphous semiconductor such as silicon or germanium, the off-current of the transistor can be reduced, and if it is a microcrystalline semiconductor, the on-current can be increased by reducing the contact resistance with the ohmic contact layer. As described above, by providing the etching stopper layer, the ohmic contact layer can be formed without establishing the technique of selectively etching the n-type semiconductor on the intrinsic semiconductor which is the active layer.

Further, the amorphous silicon film 4 is irradiated during laser irradiation.
It is also possible to increase the thickness of the film for coating and also serve as the etching stopper layer. For example, 308 nm XeCl
100 nm of microcrystalline silicon having an absorption coefficient of 1 × 10 ⁵ cm ⁻¹ for excimer laser light is deposited on the amorphous silicon film 4.
When deposited and irradiated with a XeCl excimer laser, the transmittance of the microcrystalline silicon layer for laser light is 36.7%, so if the laser power is sufficiently increased, the lower layer becomes polycrystal. In this method, amorphous silicon and microcrystalline silicon are continuously formed, so even if the atmosphere is opened during laser irradiation,
It is possible to manufacture a high-performance thin film transistor with a high on-current without causing the microcrystalline interface to be naturally oxidized and increasing the contact resistance of the interface. Here, the film covering the amorphous silicon film 4 is not limited to microcrystalline silicon, and may be any semiconductor film having a light absorption coefficient for laser smaller than amorphous silicon, a high melting point, and a high conductivity. The type is not particularly selected.

In this embodiment, the structure of the transistor is formed by patterning the chromium silicide 9 to the silicon nitride film 3 in an island pattern at a time, but the present invention is not limited to this structure. For example, it is of course applicable to a transistor having a structure in which chromium silicide 9 to amorphous silicon 4 are collectively patterned on an island.

Next, the present invention will be described with reference to CHP ( ch annel p assivat
A second embodiment applied to a method of manufacturing a thin film transistor having an ed) structure will be described. FIG. 3 shows a CH to which the present invention is applied.
It is sectional drawing which shows the manufacturing process of the thin film transistor of P structure. First, as shown in (a), Cr is deposited on the glass substrate 1 by a 1200Å sputtering method and patterned to form the gate electrode 2. Then, the plasma CVD method is applied to the source gases SiH ₄ , NH ₃ and N ₂ for 350
Silicon nitride film 3, which is the gate insulating film of 0Å 3, Si
An amorphous silicon film 4, which is an active layer of 200 to 600 Å using H ₄ and H ₂ , a microcrystalline silicon film 5 of 20 to 100 Å, which is an H ₂ large dilution condition using SiH ₄ and H _2.
A silicon nitride film 15 as an etching stopper layer of 2000 Å is continuously deposited by using ₄ , NH ₃ , and N ₂ . Next, a 220 mJ / cm ² XeCl excimer laser is irradiated in a vacuum to crystallize the amorphous silicon film 4 and the polycrystalline silicon film 6
To form. At this time, the etching stopper layer 15 hardly absorbs the laser, and if the microcrystalline silicon 5 has the same film quality and film thickness as those of the first embodiment, it absorbs only about 10% of the laser and the melting points of both layers. Is higher than amorphous silicon 4, its shape does not change. The surface roughness of the polycrystalline silicon is reduced due to the effect of the two upper layers, compared with the case where only one etching stopper layer is formed. Next, the enching stopper layer 15 is patterned into an island shape by using a hydrofluoric acid-based aqueous solution. Then, n-type amorphous silicon 8 is continuously deposited using SiH ₄ , H ₂ and PH _3, and then chromium silicide (CrSi) 9 is formed on the surface of 8. Then, the films 3 to 9 are patterned into islands. Then, a 2800 Å ITO (Indi
umTin Oxide) 10 is deposited. Next, as shown in (b), a resist 11 is applied and then formed into a predetermined shape for forming source and drain electrodes by photolithography. Then, as shown in (c), the ITO 10 is removed by wet etching with hydrobromic acid to remove the source and drain electrodes 1.
2 and 13 are formed. Then, the n-type amorphous silicon 8 is removed by the dry etching method using BCl ₃ to form the ohmic contact layer 14 to complete the thin film transistor.

According to the embodiment, since the amorphous silicon film 4 is covered with the microcrystalline silicon 5 as well as the etching stopper layer 15 at the time of laser irradiation, the polycrystalline silicon film 4 is covered more than the etching stopper layer 15 alone. It is possible to further prevent the surface roughness caused by the formation of No. 6 and the accompanying deterioration of the crystal quality. As shown by the gate voltage-drain current characteristics in FIG. 4, compared with a polycrystalline thin film transistor manufactured by irradiating a laser beam coated with an etching stopper layer alone, a high on current and a low off current have high characteristics. A transistor can be manufactured. Further, since the surface of the polycrystalline silicon 6 is covered with the microcrystalline silicon 5, when the etching stopper layer 15 is processed into an island shape by etching with the hydrofluoric acid-based aqueous solution, the hydrofluoric acid-based material is removed from the holes caused by the surface roughness. The phenomenon that the aqueous solution soaks into the polycrystalline silicon 6 and etches the gate insulating film to cause a decrease in withstand voltage does not occur.

The active layer polycrystallized by laser irradiation is not particularly limited to amorphous silicon, and the kind thereof is not particularly limited as long as it is a semiconductor which is crystallized by laser irradiation and has high conductivity. For example, 2 amorphous germanium
The amorphous germanium has a larger light absorption coefficient for the laser than the amorphous silicon when it is irradiated with a laser after the microcrystalline silicon and the etching stopper layer are continuously deposited in the same manner as in the above-mentioned embodiment. Is low, the energy of the laser can be reduced and the transistor can be manufactured at a lower process temperature. Further, the semiconductor film that covers the lower layer semiconductor during laser irradiation is not limited to microcrystalline silicon, and if the semiconductor film is smaller than the lower layer semiconductor in terms of light absorption coefficient for laser, high melting point, and high conductivity, the type of semiconductor film is Does not choose. For example, since the melting point of microcrystalline silicon carbide (SiC) is higher than that of amorphous silicon and the light absorption coefficient is smaller than that of microcrystalline silicon, amorphous silicon can be crystallized with lower laser energy and active by laser. Damage to layers can be reduced.

In the present embodiment, the structure of the transistor is patterned from the chromium silicide 9 to the silicon nitride film 3 in an island pattern at a time, but the present invention is not limited to this structure. For example, it is of course applicable to a transistor having a structure in which chromium silicide 9 to amorphous silicon 4 are collectively patterned on an island.

Next, a third embodiment in which a thin film transistor (hereinafter referred to as TFT) manufactured according to the present invention is used as a driving element for a display pixel of an active matrix type liquid crystal display device will be described.

FIG. 5 shows the configuration of an active matrix type liquid crystal display device which is an embodiment of the present invention. In the figure,
A TFT is provided for each of a plurality of liquid crystal cells (LC) arranged in a matrix, and each liquid crystal cell is driven by the switching operation of the TFT. Here, a gate voltage is sequentially applied to the gate lines G1 to GM, which are electrodes commonly drawn from the gates of the TFTs arranged in the horizontal direction on the glass substrate 1, and the gates are turned on for each gate line. Go. On the other hand, the data voltage for each turned-on gate line is sequentially applied to the drain lines D1 to DN, which are electrodes commonly drawn from the drains of the TFTs arranged in the vertical direction, and applied to each liquid crystal cell. FIG. 6 shows a planar structure of one pixel composed of one liquid crystal cell and TFT. Further, FIG. 7 shows a cross section taken along a broken line XX 'in FIG. The TFT formed near the intersection of the drain wiring D and the gate wiring G and the source electrode 12
A liquid crystal cell LC connected via the is arranged. TF
The sectional structure of T is almost the same as that of the first embodiment. This structure can be obtained by the manufacturing method described in the embodiment, but only the changes from the process are as follows. That is, the gate wiring G and the drain wiring D are formed simultaneously with the gate electrode 2 and the drain electrode 13 by film formation and etching. In addition, the parts other than the TFT such as the liquid crystal 16 will be described below. The TN type liquid crystal 16 is sealed between a glass substrate (counter substrate) 17 facing the glass substrate on which the TFT is formed. A black matrix 18 and an ITO 19 film for blocking unnecessary light rays are formed on the counter substrate. The liquid crystal is driven by the voltage between the ITO 19 of the counter substrate and the ITO of the TFT substrate, and the brightness displayed for each pixel is changed to display an image on the matrix of pixels. A deflection plate 20 for deflecting light on either of the glass substrates 1 and 17
Is attached. The deflection axes of these two deflection plates are orthogonal,
Or if they are arranged in parallel, they are normally black,
The display mode is normally white. Further, an alignment film 21 for aligning the liquid crystal is applied to the surface in contact with the liquid crystal, that is, the surface of the protective film 22 and the ITO film 10 on the glass substrate 1 side, and the surface of the ITO film on the counter substrate 17 side. The surface of the alignment film is treated by a rubbing method after coating, and is given anisotropy for aligning liquid crystal molecules. As described above, when the thin film transistor manufactured according to the present invention is used as a driving element of a display pixel of an active matrix liquid crystal display device, the size of the transistor can be reduced and the aperture ratio of the pixel can be increased because of a high on-current. As a result, the power consumption of the backlight can be reduced and the power consumption of the entire liquid crystal display device can be reduced.

Next, a description will be given of a fourth embodiment in which the crystalline thin film transistor according to the present invention is formed and used as a part (sampling circuit) of a drive circuit of an active matrix type liquid crystal display device on the same substrate as a display section. .

FIG. 8 shows the structure of an active matrix type liquid crystal display device using the present invention. In this embodiment, part of the function of the driver circuit is formed over the same glass substrate as the thin film transistor of the pixel. In the figure, thin film transistors are provided for a plurality of liquid crystal cells (LC) arranged in a matrix, and the liquid crystal cells are driven by the switching operation of the thin film transistors. Here, a gate voltage is sequentially applied from the gate drive circuit (driver IC) 23 to the gate lines G1 to GM, which are electrodes commonly drawn from the respective gates of the thin film transistors arranged in the lateral direction on the glass substrate 1, The gate is turned on for each gate line. On the other hand, to the drain lines D1 to DN, which are electrodes commonly drawn from the drains of the thin film transistors arranged in the vertical direction, the data voltage for each gate line turned on is sequentially applied from the data driving circuit 24 through the sampling circuit 25. Then, give each liquid crystal cell. Further, as shown in FIG. 9, the sampling circuit 25 has a sampling thin film transistor for each drain line, and supplies a plurality of voltages φ1 and φ2 to the gate of the sampling thin film transistor while the pixel thin film transistor gate voltage is on. . The two drain lines are grouped together and connected from the sampling circuit 25 to the data driving circuit 24. Since the sampling circuit 24 is formed on the glass substrate 1 like the thin film transistor of the pixel, the number of connections between the sampling circuit 25 and the data driving circuit 24 is halved. The drain lines D1 and D2 are integrated and connected to the data driving circuit as DK1, and as a result, the number of connections between the data driving circuit 24 and the substrate on which the pixel thin film transistors and the sampling circuit 25 are formed is reduced by half, that is, the data driving circuit is configured. The number of driver ICs used can be halved. Since the sampling circuit 25 can be easily formed in the same process as the pixel thin film transistor, it is possible to reduce the number of driver ICs by half.
The liquid crystal display cost can be reduced. The pixel thin film transistor may have a non-laser-irradiated active layer that is amorphous, or may be a polycrystalline thin film transistor. If it is amorphous, it becomes a pixel thin film transistor having excellent holding characteristics due to low off current, and if it is polycrystalline, it has a high on current, so that the size of the transistor can be made small, and a high aperture ratio or high definition of the pixel can be achieved. If the crystalline thin film transistor according to the present invention is formed on the same substrate as the display unit as a part of the drive circuit of the active matrix type liquid crystal display device, the number of driver ICs forming the data drive circuit can be reduced. It will be possible.

[0021]

According to the present invention, it is possible to prevent the surface roughness of polycrystalline silicon during laser irradiation and the accompanying deterioration of crystal quality, and to manufacture a crystalline thin film transistor with high characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of an embodiment in which the present invention is applied to manufacturing a thin film transistor.

FIG. 2 is an explanatory diagram comparing the gate voltage-drain current characteristics of a thin film transistor manufactured according to the present invention with a conventional thin film transistor in which amorphous silicon is directly irradiated with a laser.

FIG. 3 is a sectional view showing a manufacturing process of an embodiment in which the present invention is applied to manufacture of a CHP structure thin film transistor.

FIG. 4 is an explanatory diagram comparing the gate voltage-drain current characteristics of a CHP structure thin film transistor manufactured according to the present invention with that of a CHP structure thin film transistor in which amorphous silicon is irradiated with laser only through an etching stopper layer.

FIG. 5 is an explanatory diagram of an active matrix type liquid crystal display device using a thin film transistor manufactured according to the present invention as a liquid crystal cell driving element.

FIG. 6 is a plan view of one pixel including a liquid crystal cell and a thin film transistor manufactured according to the present invention.

FIG. 7 is a cross-sectional view of one pixel including a liquid crystal cell and a thin film transistor manufactured according to the present invention.

FIG. 8 is an explanatory diagram showing a configuration of an active matrix type liquid crystal display device using the present invention.

FIG. 9 is a sampling circuit diagram using the present invention.

[Explanation of symbols]

1 ... Glass substrate, 2 ... Gate electrode, 3 ... Gate insulating film,
5 ... Microcrystalline silicon film, 6 ... Polycrystalline silicon film, 7 ... Amorphous silicon film, 8 ... N-type amorphous silicon film, 9-point chrome silicide, 10 ... ITO, 11 ... Resist, 12 ...
Source electrode, 13 ... Drain electrode, 14 ... Ohmic contact layer.

Claims (18)

[Claims] 1. An inverted stagger having a gate electrode, a gate insulating film, an active layer made of a semiconductor formed on an insulating substrate, an ohmic contact layer formed by doping the semiconductor with impurities, a source electrode and a drain electrode. In a method of manufacturing a thin film transistor, when forming the active layer, a semiconductor having a smaller light absorption coefficient for the laser or a higher melting point than that of the semiconductor is stacked on the semiconductor in contact with the gate insulating film, and the laser is irradiated. A method of manufacturing a thin film transistor, comprising: 2. An inverted stagger having an gate electrode, a gate insulating film, an active layer made of a semiconductor formed on an insulating substrate, an ohmic contact layer formed by doping the semiconductor with an impurity, a source electrode, and a drain electrode. In a method of manufacturing a thin film transistor, when forming the active layer, a semiconductor having a smaller light absorption coefficient for a laser and a higher melting point than that of the semiconductor is stacked on the semiconductor in contact with the gate insulating film, and the laser is irradiated. A method of manufacturing a thin film transistor, comprising: 3. An inverted stagger having an gate electrode, a gate insulating film, an active layer made of a semiconductor, an ohmic contact layer formed by doping the semiconductor with an impurity, a source electrode, and a drain electrode formed on an insulating substrate. In a method for manufacturing a thin film transistor, when forming the active layer, a semiconductor having a smaller light absorption coefficient for laser and a higher melting point than that is stacked on an amorphous semiconductor in contact with the gate insulating film to irradiate a laser. A method of manufacturing a thin film transistor, comprising: 4. An inverted stagger, which is formed on an insulating substrate and has a gate electrode, a gate insulating film, an active layer made of a semiconductor, an ohmic contact layer formed by doping the semiconductor with an impurity, a source electrode, and a drain electrode. A method of manufacturing a thin film transistor, wherein a microcrystalline semiconductor is stacked on an amorphous semiconductor in contact with the gate insulating film and a laser is irradiated when the active layer is formed. 5. An inverted stagger, which is formed on an insulating substrate and has a gate electrode, a gate insulating film, an active layer made of a semiconductor, an ohmic contact layer formed by doping the semiconductor with an impurity, a source electrode and a drain electrode. In a method for manufacturing a thin film transistor, after forming a layer of a semiconductor having a smaller light absorption coefficient for a laser and a higher melting point than that on the semiconductor in contact with the gate insulating film, the active layer is irradiated with the laser. And a method of manufacturing a thin film transistor, which further comprises stacking semiconductors. 6. An inverted stagger including an gate electrode, a gate insulating film, an active layer made of a semiconductor, an ohmic contact layer formed by doping an impurity into the semiconductor, a source electrode, and a drain electrode formed on an insulating substrate. In a method for manufacturing a thin film transistor, after forming a layer of a semiconductor having a smaller light absorption coefficient for a laser and a higher melting point than that on the semiconductor in contact with the gate insulating film, the active layer is irradiated with the laser. And a method of manufacturing a thin film transistor, which further comprises stacking an amorphous semiconductor. 7. An inverted stagger having an gate electrode, a gate insulating film, an active layer made of a semiconductor, an ohmic contact layer formed by doping an impurity into the semiconductor, a source electrode, and a drain electrode formed on an insulating substrate. In a method for manufacturing a thin film transistor, after forming a layer of a semiconductor having a smaller light absorption coefficient for a laser and a higher melting point than that on the semiconductor in contact with the gate insulating film, the active layer is irradiated with the laser. And a method of manufacturing a thin film transistor, further comprising laminating a microcrystalline semiconductor. 8. An inverted stagger, which is formed on an insulating substrate and has a gate electrode, a gate insulating film, an active layer made of a semiconductor, an ohmic contact layer formed by doping the semiconductor with an impurity, a source electrode, and a drain electrode. In a method for manufacturing a thin film transistor, when forming the active layer, a semiconductor having a smaller light absorption coefficient for laser and a higher melting point than that is stacked on an amorphous semiconductor in contact with the gate insulating film to irradiate a laser. After that, the method for manufacturing a thin film transistor, further comprising stacking the semiconductor. 9. An inverted stagger including an gate electrode, a gate insulating film, an active layer made of a semiconductor, an ohmic contact layer formed by doping an impurity into the semiconductor, a source electrode, and a drain electrode formed on an insulating substrate. In a method of manufacturing a thin film transistor, when forming the active layer, laminating a microcrystalline semiconductor on an amorphous semiconductor in contact with the gate insulating film, irradiating a laser, and further laminating the semiconductor. A method of manufacturing a thin film transistor having the characteristics. 10. A gate electrode formed on an insulating substrate,
In a method of manufacturing an inverted stagger type thin film transistor having a gate insulating film, an active layer made of a semiconductor, an ohmic contact layer formed by doping the semiconductor with impurities, a source electrode and a drain electrode, when forming the active layer, A method of manufacturing a thin film transistor, comprising stacking a microcrystalline semiconductor on an amorphous semiconductor in contact with the gate insulating film, irradiating a laser, and then stacking the amorphous semiconductor. 11. A gate electrode formed on an insulating substrate,
In a method of manufacturing an inverted stagger type thin film transistor having a gate insulating film, an active layer made of a semiconductor, an ohmic contact layer formed by doping the semiconductor with impurities, a source electrode and a drain electrode, when forming the active layer, A method of manufacturing a thin film transistor, comprising stacking a microcrystalline semiconductor on an amorphous semiconductor in contact with the gate insulating film, irradiating a laser, and then stacking the microcrystalline semiconductor. 12. A gate electrode formed on an insulating substrate,
In a method of manufacturing an inverted stagger type thin film transistor having a gate insulating film, an active layer made of a semiconductor, an etching stopper layer made of a transparent insulating film, an ohmic contact layer formed by doping a semiconductor with impurities, a source electrode and a drain electrode, When forming the active layer, a semiconductor having a smaller light absorption coefficient for the laser and a higher melting point than that on the semiconductor in contact with the gate insulating film, and further an etching stopper layer are continuously laminated, and then the laser is irradiated. A method of manufacturing a thin film transistor, comprising: 13. A gate electrode formed on an insulating substrate,
In a method of manufacturing an inverted stagger type thin film transistor having a gate insulating film, an active layer made of a semiconductor, an ohmic contact layer formed by doping the semiconductor with impurities, a source electrode and a drain electrode, when forming the active layer, A method of manufacturing a thin film transistor, comprising stacking microcrystalline silicon on amorphous silicon in contact with the gate insulating film, irradiating a laser, and then stacking amorphous silicon. 14. Claims 1, 2, 3, 4, 5, 6, 7,
8. A method of manufacturing a thin film transistor for driving a liquid crystal cell of a liquid crystal display device, wherein a thin film transistor is used as a driving element of a liquid crystal cell that constitutes a pixel of a display portion. 15. Claims 1, 2, 3, 4, 5, 7, 8,
9. A method for manufacturing a thin film transistor for driving a display unit of a liquid crystal display device, wherein at least a part of a circuit for driving the display unit is formed on the same substrate as the display unit. 16. Claims 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 11, 12 or 13, at least a part of a circuit for driving the display unit is formed on the same substrate as the display unit, a thin film transistor for driving a liquid crystal cell of the liquid crystal display device and for driving the display unit. Manufacturing method. 17. A liquid crystal display device in which at least a part of a circuit for driving the display unit is formed on the same substrate as the display unit and includes a liquid crystal cell driving thin film transistor and a display unit driving thin film transistor. 2. A liquid crystal display device, wherein the active layer of the thin film transistor for use in the display has a laminated structure of an amorphous semiconductor and a microcrystalline semiconductor, and the active layer of the thin film transistor for driving the display unit has a laminated structure of a polycrystalline semiconductor and a microcrystalline semiconductor. 18. A liquid crystal display device in which at least a part of a circuit for driving the display unit is formed on the same substrate as the display unit and includes a liquid crystal cell driving thin film transistor and a display unit driving thin film transistor. The active layer of the thin film transistor has a laminated structure of an amorphous semiconductor, a microcrystalline semiconductor and an amorphous semiconductor, and the active layer of the display driving thin film transistor has a laminated structure of a polycrystalline semiconductor, a microcrystalline semiconductor and an amorphous semiconductor. A liquid crystal display device characterized by the above.