JP2001326360A - Method for manufacturing active matrix substrate, active matrix substrate and method for manufacturing thin film field-effect transistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an active matrix substrate by which a cost can be reduced and reliability can be enhanced. SOLUTION: An island-like semiconductor region 130 is formed by selective etching by use of the same mask on a gate insulation film 102. A transparent conductive film and a conductive film are continuously deposited on the entire surface of a substrate, and a signal wiring, a source electrode 107, a drain electrode 106 and a pixel electrode 105 are formed by the selective etching by use of the same mask. A part of the island-like semiconductor region 130 is removed by etching with the source electrode 107 and the drain electrode 106 as a mask, and a channel part 109 is formed. Thereafter, a hydrogen plasma processing is carried on in the channel part 109 to form a plasma irradiation region 112. And, a protection insulation film 110 is deposited on the entire surface of the substrate, and the selective etching is performed in the regions of the conductive film and the protection insulation film 110 on the pixel electrode 105 by use of the same mask to form a pixel electrode opening part 111.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for manufacturing an active matrix substrate and a method for manufacturing an active matrix substrate and a thin film field effect transistor.

[0002]

2. Description of the Related Art Conventionally, as an electronic device using a thin film field effect transistor, there is a liquid crystal display device. This liquid crystal display device has an active device on which a plurality of thin film field effect transistors are mounted. It has a matrix substrate.

A method of manufacturing the active matrix substrate will be described. First, as shown in FIG. 4, a scanning wiring 201 and a gate insulating film 202 made of a conductive metal film such as Ta are formed on a transparent insulating substrate 200 by a photolithography process and etching. After patterning by a process or the like, an a-Si film (intrinsic semiconductor film 203, conductive semiconductor film 204) is deposited on the gate insulating film 202, and an island-like active layer 220 is formed by patterning. A transparent conductive film of ITO (tin-added indium oxide) or the like and a conductive metal film of Ta or the like are successively laminated on the active layer 220, and then a signal wiring 208, a source electrode 207 and a drain electrode are formed using a predetermined mask. Step 206 is formed. Thereafter, the pixel electrodes 205 are similarly patterned using a mask.

Subsequently, an n + type a- layer is formed using the source electrode 207 and the drain electrode 206 made of a conductive metal film as a mask.
A channel portion 209 is formed by etching Si (conductive semiconductor film 204) (Japanese Patent Laid-Open No. 60-42).
868).

Further, a protective insulating film 210 made of a silicon nitride film or the like is formed so as to cover the signal wiring 208, the source electrode 207, the drain electrode 206 and the picture element electrode 205.
Are laminated, and only the protective insulating film 210 on the pixel electrodes 205 is removed using a predetermined mask.
Form one.

The pixel electrode 205 formed of a transparent conductive film made of ITO or the like is once covered with a protective insulating film 210 made of a silicon nitride film or the like during the manufacturing process. Film (pixel electrode 205)
The ITO film is reduced by contact with the
Resistance increases, or silicon nitride film etc.
There is a problem that the compound formed by reacting with the film (the pixel electrode 205) becomes difficult to remove by etching.

Further, in the method of manufacturing the active matrix substrate, the transparent conductive film forming the picture element electrode 205 and the conductive metal film forming the signal wiring 208, the source electrode 207 and the drain electrode 206 are formed using different masks. This requires a large number of photolithography steps to form a resist pattern, which is a significant factor in the manufacturing process.

In a thin-film field-effect transistor using a semiconductor film such as a-Si, when a channel portion is dug by using a source electrode and a drain electrode as a mask, the channel portion is very sensitive to a surrounding electric field. Therefore, it greatly affects the off characteristics of the thin film field effect transistor. Therefore, a protective insulating film is laminated to protect the channel portion. When the thickness of the protective insulating film is reduced, cost reduction such as shortening of the etching time for etching the protective insulating film and the conductive metal film on the pixel electrode and the lamination time of the protective insulating film can be expected. However, when the thickness of the protective insulating film is reduced, the channel portion is easily affected by the surrounding electric field, and the transistor characteristics are deteriorated.

In order to prevent a reduction reaction due to contact between a protective insulating film made of a silicon nitride film or the like and a picture element electrode made of ITO, as shown in FIGS.
8, a molybdenum 29 as a metal film is laminated, and an inorganic protective film 32 made of a silicon nitride film is formed on the molybdenum 29.
Is formed by direct contact between the silicon nitride film forming the inorganic protective film 32 and the ITO film 28.
Some prevent the reduction reaction of the membrane (Japanese Patent Application Laid-Open No. 62-28
No. 3319). However, there is a problem that the number of masks increases because the source electrode and the drain electrode, the metal film, and the pixel electrode are patterned using different masks. In addition, since the source electrode and the drain electrode, the metal film, and the pixel electrode are formed of different conductive films, a large number of film forming steps such as sputtering are required, and the connection resistance between the drain and the pixel electrode is reduced. Also increase.

It is an object of the present invention to shorten the manufacturing process and to reduce the thickness of the protective insulating film.
An object of the present invention is to provide a method of manufacturing an active matrix substrate that can reduce costs and improve reliability.

[0011]

In order to achieve the above object, a method of manufacturing an active matrix substrate according to the present invention comprises the steps of: forming a gate electrode and a scanning wiring connected to the gate electrode on a transparent insulating substrate; A step of forming a gate insulating film on the entire surface of the substrate on which the gate electrode and the scanning wiring are formed; and forming the same intrinsic semiconductor film and conductive semiconductor film as an active layer continuously deposited on the gate insulating film. Forming an island-shaped semiconductor region above the gate electrode by selective etching using a mask;
By selectively etching the transparent conductive film and the conductive film continuously deposited on the entire surface of the substrate on which the island-shaped semiconductor region is formed using the same mask, the signal wiring, the source electrode, the drain electrode, and the picture element are formed. Forming an electrode, and removing a portion of the island-shaped semiconductor region by etching using the source electrode and the drain electrode as a mask to form a channel portion made of an intrinsic semiconductor in the island-shaped semiconductor region. Forming the channel portion in the island-shaped semiconductor region, and then depositing a protective insulating film on the entire surface of the substrate;
A pixel electrode opening patterned to have substantially the same shape as the pixel electrode by removing the region of the conductive film and the region of the protective insulating film covering the pixel electrode by selective etching using the same mask. Forming a portion.

According to the method of manufacturing an active matrix substrate having the above structure, in the step of forming a gate electrode and a scanning wiring connected to the gate electrode on a transparent insulating substrate, a mask (first) is used, The same mask (second) is used for the intrinsic semiconductor film and the conductive semiconductor film, which are to be active layers, continuously deposited on the gate insulating film formed on the entire surface of the substrate on which the gate electrode and the scanning wiring are formed. Then, an island-shaped semiconductor region is formed by selective etching. After that, the gate insulating film is masked with a predetermined mask (third).
Is patterned using. Next, the transparent conductive film and the conductive film continuously deposited on the entire surface of the substrate on which the island-shaped semiconductor regions are formed are selectively etched using the same mask (fourth), so that the signal wiring is formed. Then, a source electrode, a drain electrode and a picture element electrode are formed. Using the source electrode and the drain electrode as a mask, a part of the island-shaped semiconductor region is removed by etching to form a channel portion made of an intrinsic semiconductor. Then, after a channel portion is formed in the island-shaped semiconductor region, a protective insulating film is deposited on the entire surface of the substrate, and the region of the conductive film covering the pixel electrode and the region of the protective insulating film are made of the same mask. By removing by (5th) selective etching, a pixel electrode opening patterned into substantially the same shape as the pixel electrode is formed. As described above, the conductive metal film and the transparent conductive film forming the signal wiring, the source electrode, the drain electrode, and the pixel electrode are patterned into the same shape by the same mask, and further, the protective insulating film and the conductive film on the pixel electrode are formed. Are patterned into the same shape using the same mask, the number of photolithography steps (5 masks) can be reduced, and the manufacturing process can be shortened. Further, the reliability can be improved without increasing the resistance value of the pixel electrode due to contact between the pixel electrode made of a transparent conductive film and the protective insulating film.

In one embodiment of the present invention, a method of manufacturing an active matrix substrate includes a step of performing a hydrogen plasma treatment on the channel portion formed in the island-shaped semiconductor region to form a defect introduction region. I have.

According to the method of manufacturing the active matrix substrate of the above embodiment, the channel portion formed in the island-shaped semiconductor region is subjected to the hydrogen plasma treatment to form the defect introduction region, whereby the defect of the channel portion is formed. An electric charge is fixed to the defect in the introduction region, and an external electric field is prevented by the fixed electric charge. As a result, the protective insulating film deposited on the entire substrate after the channel portion is formed in the island-shaped semiconductor region can be made thinner than in the conventional device in which the channel portion is not provided with a defect introduction region. The lamination time of the insulating film and the etching time can be shortened, and the manufacturing process can be further shortened. Further, during the hydrogen plasma treatment, since the conductive film covers the pixel electrode made of a transparent conductive film, the transmittance of the transparent conductive film of the pixel electrode does not decrease due to the reduction reaction of the hydrogen plasma, Reliability can be improved.

Further, an active matrix substrate according to the present invention is provided such that a gate electrode formed on a transparent insulating substrate, a scanning line connected to the gate electrode, and an entire surface of the substrate on which the gate electrode and the scanning line are formed. A gate insulating film, and an island-shaped semiconductor region formed above the gate electrode by patterning an intrinsic semiconductor film and a conductive semiconductor film which are to be active layers continuously deposited on the gate insulating film. And a signal wiring formed by patterning a transparent conductive film and a conductive film continuously deposited on the entire surface of the substrate on which the island-shaped semiconductor is formed, a source electrode, a drain electrode, and a pixel electrode; A part of the island-shaped semiconductor region is removed by using the source electrode and the drain electrode as a mask to form a channel made of an intrinsic semiconductor formed in the island-shaped semiconductor region. And a protective insulating film formed on the entire surface of the substrate in which the channel portion is formed in the island-shaped semiconductor region, a region of the conductive film covering the pixel electrode, and a region of the protective insulating film. And a pixel electrode opening formed as described above.

According to the active matrix substrate having the above structure, the conductive metal film and the transparent conductive film forming the signal wiring, the source electrode, the drain electrode and the picture element electrode are patterned into the same shape by the same mask. By patterning the protective insulating film and the conductive metal film in the same shape using the same mask, the number of photolithography steps can be reduced, the manufacturing process can be shortened, and the cost can be reduced. Further, the reliability can be improved without increasing the resistance value of the pixel electrode due to contact between the pixel electrode made of a transparent conductive film and the protective insulating film.

In one embodiment of the present invention, the active matrix substrate includes a defect introduction region formed by performing a hydrogen plasma process on the channel portion of the island-shaped semiconductor region.

According to the active matrix substrate of the above embodiment, the charges are fixed to the defects in the defect introduction regions formed by performing the hydrogen plasma treatment on the channel portions formed in the island-shaped semiconductor regions, and the fixed charges are fixed. Hampers the external electric field. This makes it possible to reduce the thickness of the protective insulating film that protects the channel portion as compared with a conventional device in which the defect introduction region is not provided in the channel portion, thereby shortening the lamination time of the protective insulating film and the etching time. In addition, the manufacturing process can be further shortened. Further, during the hydrogen plasma treatment, since the conductive film covers the pixel electrode made of a transparent conductive film, the transmittance of the transparent conductive film of the pixel electrode does not decrease due to the reduction reaction of the hydrogen plasma, Reliability can be improved.

Further, in the method of manufacturing a thin film field effect transistor according to the present invention, a step of forming a gate electrode on an insulating substrate, a step of forming a gate insulating film on the entire surface of the substrate on which the gate electrode is formed, A step of continuously depositing an intrinsic semiconductor film and a conductive semiconductor film to be an active layer over the entire surface of the substrate on which the insulating film is formed, and selectively etching the intrinsic semiconductor film and the conductive semiconductor film to form A step of forming an island-shaped semiconductor region above the gate electrode; a step of continuously depositing a transparent conductive film and a conductive film over the entire surface of the substrate on which the island-shaped semiconductor region is formed; Forming a source electrode and a drain electrode above the island-shaped semiconductor region by selectively etching the conductive film and the conductive film; and forming an upper electrode using the source electrode and the drain electrode as a mask. Removing a part of the island-shaped semiconductor region by etching to form a channel portion made of an intrinsic semiconductor in the island-shaped semiconductor region; and forming a hydrogen plasma on the channel portion formed in the island-shaped semiconductor region. Performing a process to form a defect introduction region.

According to the method of manufacturing the thin-film field-effect transistor having the above-described structure, the channel portion formed in the island-shaped semiconductor region is subjected to hydrogen plasma treatment to form a defect introduction region in the channel portion. The electric charge is fixed to the defect in the defect introduction region of the channel portion, and the fixed electric charge prevents an external electric field. This makes it possible to make the protective insulating film for protecting the channel portion thinner than a conventional device in which no defect introduction region is provided in the channel portion. Therefore, the lamination time of the protective insulating film and the etching time can be shortened, so that the manufacturing process can be shortened and the cost can be reduced. In addition, the resistance of the pixel electrode does not increase due to the contact between the pixel electrode made of the transparent conductive film and the protective insulating film, and the transmittance of the transparent conductive film of the pixel electrode does not decrease due to the reduction reaction of the hydrogen plasma. , Reliability can be improved.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing an active matrix substrate and a method for manufacturing an active matrix substrate and a thin film field effect transistor according to the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 is a cross-sectional view of a main part of an active matrix substrate manufactured by using a method of manufacturing an active matrix substrate according to an embodiment of the present invention, wherein 100 is an insulating substrate, 101 is a gate electrode, 102 Is a gate insulating film, 103 is an intrinsic conductive film, 104 is a conductive conductive film, 10
5 is a picture element electrode, 106 is a drain electrode, and 107 is a source electrode.

FIGS. 2A to 2C are cross-sectional views of a main part of the active matrix substrate for explaining the method of manufacturing the active matrix substrate according to the present invention.
A description will be given according to (a) to (c).

First, as shown in FIG. 2A, the thickness is 1.1 m.
A Ta, Al or Al alloy film or the like is deposited on an insulating substrate 100 such as a non-alkali glass plate by sputtering or the like, and is subjected to a photolithography process and an etching process to form the scanning wiring 120 (FIG. 3).
And a gate electrode 101 connected to it is formed.

Next, a gate insulating film 102 made of SiNx is formed on the gate electrode 101.

Subsequently, an intrinsic conductor film 103 made of a non-doped a-Si film or the like and an n + type a-Si film doped with phosphorus are used.
A conductive semiconductor film 104 made of a film or the like is continuously laminated, and is patterned in an island shape on the gate electrode 101 through a photolithography process and an etching process to form a semiconductor layer (the island-shaped semiconductor region 130). .

Next, a transparent conductive film made of ITO or the like is formed on the entire surface of the substrate by sputtering, and a Ta film, which is a conductive metal film, is further laminated thereon by a sputtering method. 106, source electrode 1
07 and the pattern of the pixel electrode 105,
A resist pattern is formed by photolithography. Then, the Ta film is first dry-etched to form the signal wiring 108, the drain electrode 106, and the source electrode 10.
After the formation of 7, the ITO film is wet-etched using the same resist pattern to continuously pattern the transparent conductive film, thereby forming the pixel electrode 105.
At this time, the conductive metal film (the signal wiring 108, the drain electrode 106, and the source electrode 1) laminated on the transparent conductive film
07) is not limited to Ta, and may be a single-layer film such as Mo or Ti or a laminated film such as Al / Ti or Ta / TaN.

Next, using the drain electrode 106 and the source electrode 107 made of Ta as a mask, the island-shaped semiconductor region 13 is formed.
The upper portions of the n + type a-Si film and the a-Si film of 0 are removed by etching to form a channel portion 109.

Further, the flow rate of H ₂ gas is 2000 sccm,
Pressure 1200mT, output 600W, electrode distance 1200m
il, a-S of channel unit 109 in processing time 30 sec
The i-film surface is irradiated with hydrogen plasma to form a hydrogen plasma irradiation region 112 as a defect introduction region (see FIG. 2B).

Subsequently, SiNx is laminated as a protective insulating film 110 on the entire surface of the substrate, and a resist pattern for forming the pixel electrode opening 111 is formed by a photolithography process. Electrode 10
5, a pixel upper metal film 106a made of a conductive metal film of Ta or the like (a region 106b on the periphery of the pixel electrode 105).
) And dry etching at the same time.
5 is formed on the pixel electrode 5 (FIG. 2 (c), FIG.
reference).

As described above, the transparent conductive film forming the picture element electrode 105 and the conductive metal film forming the signal wiring 108, the source electrode 107, and the drain electrode 106 are patterned with the same mask, whereby the transparent conductive film is formed. Is covered with the pixel upper metal film 106a made of a conductive metal film, the reduction of the transparent conductive film (pixel electrode 105) does not occur even if the hydrogen plasma treatment is performed,
The hydrogen plasma treatment is performed only on the hydrogen plasma irradiation region 112 of the channel portion 109, so that a process for introducing a defect into the surface of the channel portion 109 can be performed. Therefore, the protective insulating film 110 can be thinly stacked while preventing deterioration in characteristics such as leakage current flowing in the channel portion.

Further, by laminating the protective insulating film 110 thinly, the pixel upper metal film 106a and the protective insulating film 1 are formed.
When the pixel electrode opening 111 is formed on the substrate 10, etching can be performed continuously using the same mask, and the etching time can be reduced.

At the same time, the picture element electrode 105 and the signal wiring 1
08, the conductive metal film forming the source electrode 107 and the drain electrode 106 and the transparent conductive film are patterned with the same mask, so that the number of masks can be reduced and the manufacturing process can be shortened by reducing the number of photolithography steps.

In the above embodiment, the active matrix substrate using the thin film field effect transistor has been described. However, the method of manufacturing a thin film field effect transistor according to the present invention may be applied to all devices using the thin film field effect transistor. .

[0035]

As is clear from the above, according to the method for manufacturing an active matrix substrate and the active matrix substrate of the present invention, the conductive metal film forming the picture element electrode, the signal wiring, the source electrode and the drain electrode is transparent. Pattern the conductive film and the same shape with the same mask,
Furthermore, by patterning the protective insulating film and the conductive metal film on the pixel electrodes into the same shape with the same mask,
The number of photolithography steps can be reduced, and the manufacturing process can be shortened.

According to the method for manufacturing an active matrix substrate and the active matrix substrate, the channel portion of the island-shaped semiconductor region is subjected to the hydrogen plasma treatment, whereby the thickness of the protective insulating film can be reduced. In addition to shortening the lamination time and the etching time, the manufacturing cost is improved by improving the etching processing ability without deteriorating the transistor characteristics or reducing the transmittance of the transparent conductive film of the pixel electrode due to the reduction reaction of hydrogen plasma. And the reliability can be reduced.

According to the method of manufacturing a thin film field effect transistor of the present invention, the channel portion formed in the island-shaped semiconductor region is subjected to hydrogen plasma treatment to form a defect introduction region in the channel portion. By preventing an external electric field by the fixed charge in the defect introduction region, the protective insulating film for protecting the channel portion can be made thinner than in the conventional device having no defect introduction region in the channel portion. The stacking time and the etching time can be shortened, the manufacturing process can be shortened, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of an active matrix substrate manufactured by using an active matrix substrate manufacturing method according to an embodiment of the present invention.

FIGS. 2A to 2C are cross-sectional views of main parts of the active matrix substrate for describing a method of manufacturing the active matrix substrate.

FIG. 3 is a plan view of the active matrix substrate.

FIG. 4 is a sectional view of a main part of a conventional active matrix substrate.

FIG. 5 is a cross-sectional view of a main part of another conventional active matrix substrate.

[Explanation of symbols]

 Reference Signs List 100: insulating substrate, 101: gate electrode, 102: gate insulating film, 103: intrinsic semiconductor film, 104: conductive semiconductor film, 105: picture element electrode, 106: drain electrode, 106a: picture element upper metal film, 107 ... source electrode, 108 ... signal wiring, 109 ... channel part, 110 ... protective insulating film, 111 ... picture element electrode opening, 112 ... hydrogen plasma irradiation area, 120 ... scanning wiring, 130 ... island-shaped semiconductor area.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 29/78 627E F-term (Reference) 2H092 JA26 JA29 JA38 JA42 JA44 JA47 JB13 JB23 JB32 JB33 JB38 JB51 JB57 JB63 JB69 KA05 KA07 KA12 KA16 KA18 KB24 MA05 MA08 MA14 MA15 MA16 MA18 MA19 MA20 MA27 MA35 MA37 MA41 NA25 NA27 NA29 5C094 AA31 AA43 AA44 BA03 BA43 CA19 CA24 DA14 DA15 EA04 EA07 EB02 FB12 FB14 FB15 5F04 DB01 DB08 DB30 DB01 FA08 EE03 EE04 EE06 EE44 FF03 GG02 GG15 GG35 HK01 HK03 HK04 HK07 HK09 HK16 HK21 HK22 HK25 HK33 HK39 NN02 NN24 NN72 QQ25

Claims (5)

[Claims] A step of forming a gate electrode and a scanning wiring connected to the gate electrode on a transparent insulating substrate; and a step of forming a gate insulating film on the entire surface of the substrate on which the gate electrode and the scanning wiring are formed. An island-shaped semiconductor region is formed above the gate electrode by selectively etching the intrinsic semiconductor film and the conductive semiconductor film which are to be active layers continuously deposited on the gate insulating film using the same mask. A signal wiring, a source electrode, and a drain by selectively etching the transparent conductive film and the conductive film continuously deposited on the entire surface of the substrate on which the island-shaped semiconductor region is formed using the same mask. Forming an electrode and a pixel electrode; removing the island-shaped semiconductor region by etching using the source electrode and the drain electrode as a mask; Forming a channel portion made of an intrinsic semiconductor in frequency, after forming the channel portion to the island-shaped semiconductor region,
Depositing a protective insulating film over the entire surface of the substrate, and removing the region of the conductive film and the region of the protective insulating film covering the pixel electrode by selective etching using the same mask, thereby forming the pixel electrode Forming a pixel electrode opening patterned to have substantially the same shape as that of the active matrix substrate. 2. The method for manufacturing an active matrix substrate according to claim 1, further comprising a step of performing a hydrogen plasma treatment on the channel portion formed in the island-shaped semiconductor region to form a defect introduction region. A method for manufacturing an active matrix substrate. 3. A gate electrode formed on a transparent insulating substrate and a scanning line connected to the gate electrode; a gate insulating film formed on the entire surface of the substrate on which the gate electrode and the scanning line are formed; An island-shaped semiconductor region formed above the gate electrode by patterning the intrinsic semiconductor film and the conductive semiconductor film which are to be active layers continuously deposited on the insulating film; and A signal wiring, a source electrode, a drain electrode, and a picture element electrode formed by patterning a transparent conductive film and a conductive film continuously deposited on the entire surface of the formed substrate, and masking the source electrode and the drain electrode. Removing a part of the island-shaped semiconductor region to form a channel portion made of an intrinsic semiconductor formed in the island-shaped semiconductor region; A protective insulating film formed on the entire surface of the substrate on which the pixel portion is formed, and a pixel electrode opening formed by removing the conductive film region and the protective insulating film region covering the pixel electrode. An active matrix substrate, comprising: 4. The active matrix substrate according to claim 3, further comprising a defect introduction region formed by subjecting said channel portion of said island-shaped semiconductor region to hydrogen plasma processing. . 5. A step of forming a gate electrode on an insulating substrate, a step of forming a gate insulating film on the entire surface of the substrate on which the gate electrode is formed, and forming an active layer on the entire surface of the substrate on which the gate insulating film is formed. Successively depositing an intrinsic semiconductor film and a conductive semiconductor film, and forming an island-shaped semiconductor region above the gate electrode by selectively etching the intrinsic semiconductor film and the conductive semiconductor film A step of continuously depositing a transparent conductive film and a conductive film over the entire surface of the substrate on which the island-shaped semiconductor region is formed; and selectively etching the transparent conductive film and the conductive film. A source electrode is provided above the island-shaped semiconductor region,
Forming a drain electrode, and forming a channel portion made of an intrinsic semiconductor in the island-shaped semiconductor region by removing a part of the island-shaped semiconductor region by etching using the source electrode and the drain electrode as a mask. And performing a hydrogen plasma treatment on the channel portion formed in the island-shaped semiconductor region to form a defect-introduced region.