Semiconductor devices

Abstract

The subject of the present invention is to prevent the change of the characteristics of the TFT caused by the metal electrode depriving the oxide semiconductor film of oxygen in a semiconductor device using an oxide semiconductor TFT. In order to solve this problem, the present invention adopts the following structure. The semiconductor device is characterized in that it has a TFT, the TFT has a gate insulating film (105) formed on the gate electrode (104), an oxide semiconductor film (106) is formed on the above-mentioned gate insulating film (105), and the above-mentioned oxide semiconductor film (106) has a channel region (1061), a drain region (1063), and a source region (1064). In a top view, a metal nitride film (10) is formed on the upper surface of the above-mentioned gate electrode, in a portion opposite to the above-mentioned channel region (1061) of the above-mentioned oxide semiconductor film (106), and the above-mentioned metal nitride film (10) does not exist on a portion of the upper surface of the above-mentioned gate electrode (104).

Description

Technical Field

[0001] The present invention relates to a semiconductor device including a display device and a photosensor device using a TFT based on an oxide semiconductor. Background Art

[0002] TFT (Thin Film Transistor) using oxide semiconductors can increase OFF resistance compared to TFT using polycrystalline silicon, and can increase mobility compared to TFT using a-Si (amorphous silicon). Therefore, it can be used in display devices such as liquid crystal display devices and organic EL display devices or semiconductor devices such as sensors.

[0003] In semiconductor devices using TFTs, Al wiring is often used for the drain electrode, source electrode, image signal line, scanning line, etc. of the TFT. This is because it can reduce wiring resistance. However, Al wiring is prone to disconnection due to electromigration or stress migration. In order to prevent this, Patent Document 1 describes a structure in which the Al wiring is covered with titanium nitride (TiN).

[0004] In addition, in the semiconductor device as described above, ITO (Indium Tin Oxide) as a transparent metal oxide conductive film is used together with Al wiring. If ITO is directly connected to Al wiring, Al takes away oxygen from ITO, and the connection between Al wiring and ITO is no longer generated. In order to prevent this phenomenon, a structure in which Al wiring is set as a three-layer structure of Ti, Al, and TiN is described in the comparative example of Patent Document 2.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 6-291119

[0008] Patent Document 2: Japanese Patent Application Publication No. 2012-43821 Summary of the invention

[0009] When the oxide semiconductor is deoxidized, it will be metallized and conductive. In addition, in a TFT using an oxide semiconductor, if the channel region is deoxidized, the TFT will be turned on and will no longer operate as a TFT.

[0010] On the other hand, in a semiconductor device using TFT, metal is used for the gate electrode, drain electrode, source electrode, etc. of the TFT. Metal has the property of depriving oxygen. In a bottom-gate type oxide semiconductor TFT, there is a gate insulating film on the gate electrode, and there is an oxide semiconductor film on the gate insulating film. In such a structure, the gate electrode as a metal deprives oxygen from the oxide semiconductor via the gate insulating film, resulting in a phenomenon in which the oxide semiconductor TFT no longer works.

[0011] An object of the present invention is to prevent, in an oxide semiconductor TFT in particular, a phenomenon in which the oxide semiconductor TFT ceases to operate due to oxygen being taken away from an oxide semiconductor constituting a channel region.

[0012] The present invention overcomes the above problems, and the specific scheme is as follows.

[0013] (1) A semiconductor device comprising a TFT, wherein a gate insulating film is formed on a gate electrode, and an oxide semiconductor film is formed on the gate insulating film. The semiconductor device is characterized in that the oxide semiconductor film has a channel region, a drain region, and a source region, and in that a metal nitride film is formed on the upper surface of the gate electrode in a portion opposite to the channel region of the oxide semiconductor film in a plan view, and the metal nitride film does not exist on a portion of the upper surface of the gate electrode.

[0014] (2) In the semiconductor device described in (1) above, the metal nitride film is not present on portions of the upper surface of the gate electrode corresponding to the drain region and the source region of the oxide semiconductor film in a plan view.

[0015] (3) In the semiconductor device described in (1) above, it is characterized in that the above-mentioned oxide semiconductor film has an intermediate resistance region between the above-mentioned channel region and the above-mentioned drain region, and between the above-mentioned channel region and the above-mentioned source region, the above-mentioned metal nitride film is not formed on the portion of the upper surface of the above-mentioned gate electrode corresponding to the above-mentioned intermediate resistance region of the above-mentioned oxide semiconductor film, and the above-mentioned metal nitride film is formed on the portion corresponding to the above-mentioned drain region and the above-mentioned source region of the above-mentioned oxide semiconductor film.

[0016] (4) In the semiconductor device described in (1) above, the metal nitride film is also formed on the side surface of the gate electrode.

[0017] (5) In the semiconductor device described in any one of (1) to (4) above, a metal oxide film is formed instead of the metal nitride film.

[0018] (6) In the semiconductor device described in any one of (1) to (4) above, an insulating metal oxide film is formed instead of the metal nitride film. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a top view of a liquid crystal display device.

[0020] Figure 2 FIG. 1 is a top view of a display area of ​​a liquid crystal display device.

[0021] Figure 3 is a cross-sectional view of a display region of a liquid crystal display device.

[0022] Figure 4 This is a cross-sectional view of the vicinity of the TFT in the first mode of Example 1.

[0023] Figure 5 This is an example of the cross-sectional structure of the gate electrode of Example 1.

[0024] Figure 6 This is a cross-sectional view of the vicinity of the TFT according to the second aspect of the first embodiment.

[0025] Figure 7 This is a cross-sectional view of the vicinity of the TFT according to the third aspect of the first embodiment.

[0026] Figure 8 This is a cross-sectional view of the vicinity of the TFT according to the fourth aspect of the first embodiment.

[0027] Fig. 9 This is a cross-sectional view of the vicinity of the TFT in the first mode of Example 2.

[0028] Fig.10 This is a cross-sectional view of the vicinity of the TFT in the second mode of Example 2.

[0029] Fig.11 This is a cross-sectional view of the vicinity of the TFT in the third mode of the second embodiment.

[0030] Fig.12 This is a cross-sectional view of the vicinity of the TFT of the fourth mode of Example 2.

[0031] Fig.13 This is a cross-sectional view of the vicinity of the TFT in the first mode of Example 3.

[0032] Fig.14 This is a cross-sectional view of the vicinity of the TFT in the second mode of Example 3.

[0033] Fig.15 This is a cross-sectional view of the vicinity of the TFT of the third mode of Example 3.

[0034] Fig.16This is a cross-sectional view of the vicinity of the TFT of the fourth mode of the third embodiment.

[0035] Fig.17 This is a cross-sectional view of the vicinity of the TFT in the first mode of Example 4.

[0036] Fig.18 This is a cross-sectional view of the vicinity of the TFT in the second mode of Example 4.

[0037] Fig.19 It is a cross-sectional view of the vicinity of a TFT in a comparative example.

[0038] Fig. 20 It is a detailed cross-sectional view of a comparative example.

[0039] Fig.21 It is another detailed cross-sectional view of a comparative example. DETAILED DESCRIPTION

[0040] Hereinafter, the present invention will be described in detail by taking a liquid crystal display device as an example. Figure 1 FIG. 1 is a top view of a liquid crystal display device as an example to which the present invention is applied. Figure 1 In the embodiment, the TFT substrate 100 and the counter substrate 200 are bonded together by a sealant 16, and a liquid crystal layer is sandwiched between the TFT substrate 100 and the counter substrate 200. A display region 14 is formed in a portion where the TFT substrate 100 and the counter substrate 200 overlap.

[0041] In the display area 14 of the TFT substrate 100, the scanning lines 11 extend in the horizontal direction (x direction) and are arranged in the vertical direction (y direction). In addition, the image signal lines 12 extend in the vertical direction and are arranged in the horizontal direction. The area surrounded by the scanning lines 11 and the image signal lines 12 is a pixel 13.

[0042] The TFT substrate 100 is formed larger than the counter substrate 200, and the portion of the TFT substrate 100 that does not overlap with the counter substrate 200 is a terminal region 15. A flexible wiring substrate 17 is connected to the terminal region 15. A driver IC for driving the liquid crystal display device is mounted on the flexible wiring substrate 17.

[0043] Since liquid crystal itself does not emit light, a backlight is arranged behind the TFT substrate 100. The liquid crystal display panel controls light from the backlight for each pixel to form an image. The flexible wiring substrate 17 is bent toward the back of the backlight to reduce the overall size of the liquid crystal display device.

[0044] In the liquid crystal display device of the present invention, TFTs using oxide semiconductors with little leakage current are used for the TFTs used in the display region 14. In addition, in the edge portion near the sealing material, for example, a scan line driving circuit is formed, and for the scan line driving circuit, TFTs using polysilicon semiconductors with large mobility are mostly used, but TFTs based on oxide semiconductors can also be used.

[0045] Figure 2 is a top view of the pixels in the display area. Figure 2 This is a liquid crystal display device using the FFS (Fringe Field Switching) method in the IPS (In Plane Switching) method. Figure 2 In the embodiment of the present invention, a bottom-gate TFT using the oxide semiconductor 106 is used. The oxide semiconductor TFT has a small leakage current and is therefore suitable as a switching TFT.

[0046] exist Figure 2 In the embodiment, the scanning lines 11 extend in the horizontal direction (x direction) and are arranged in the vertical direction (y direction). In addition, the image signal lines 12 extend in the vertical direction and are arranged in the horizontal direction. A pixel electrode 116 is formed in the area surrounded by the scanning lines 11 and the image signal lines 12. Figure 2 In the embodiment, an oxide semiconductor TFT having an oxide semiconductor 106 is formed between the image signal line 12 and the pixel electrode 116. In the oxide semiconductor TFT, the image signal line 12 constitutes a drain electrode 107, and the scanning line 11 is branched and constitutes a gate electrode 104 of the oxide semiconductor TFT. The source electrode 108 of the oxide semiconductor TFT extends toward the pixel electrode 116 side and is connected to the pixel electrode 116 via the through hole 112.

[0047] The pixel electrode 116 is formed in a comb-tooth shape. The pixel electrode 116 has a slit 1161. A common electrode 113 is formed in a planar shape on the lower side of the pixel electrode 116 via a capacitor insulating film. The common electrode 113 is connected to each pixel and formed in common. If an image signal is supplied to the pixel electrode 116, electric lines of force passing through the liquid crystal layer are generated between the pixel electrode 116 and the common electrode 113, and an image is formed by rotating the liquid crystal molecules.

[0048] Figure 3 is with Figure 2 An example of a cross-sectional view of a corresponding liquid crystal display device. Figure 3 In the embodiment of the present invention, a bottom-gate TFT using the oxide semiconductor film 106 is used. The oxide semiconductor TFT has a small leakage current and is therefore suitable as a switching TFT.

[0049] Oxide semiconductors include IGZO (Indium Gallium Zinc Oxide), ITZO (Indium Tin Zinc Oxide), ZnON (Zinc Oxide Nitride), and IGO (Indium Gallium Oxide). In this embodiment, IGZO is used as the oxide semiconductor.

[0050] exist Figure 3 In the process, a polyimide substrate 100 is formed on a glass substrate 90. At the end of the process, when the glass substrate 90 is peeled off from the polyimide substrate 100, the liquid crystal display device becomes a flexible liquid crystal display device. On the polyimide substrate 100, a bottom film consisting of three layers is formed: a first bottom film 101 formed of silicon oxide (SiO), a second bottom film 102 formed of silicon nitride (SiN), and a third bottom film 103 formed of silicon oxide (SiO).

[0051] A gate electrode 104 is formed on the third base film 103. The gate electrode 104 has a stacked structure of Ti and Al. A gate insulating film 105 covers the gate electrode 104 and is formed of SiO, and an oxide semiconductor film 106 is formed on the gate insulating film 105. A drain electrode 107 is stacked on one end of the oxide semiconductor film 106, and a source electrode 108 is stacked on the other end of the oxide semiconductor film 106. The drain electrode 107 and the source electrode 108 are both formed of metal or alloy.

[0052] A first interlayer insulating film 109 made of SiO is formed to cover the oxide semiconductor 106, the drain electrode 107, and the source electrode 108, and a second interlayer insulating film 110 made of SiN is formed thereon. The first interlayer insulating film 109 is formed of SiO to supply oxygen to the channel region of the oxide semiconductor 106 from SiO.

[0053] An organic passivation film 111 is formed of, for example, acrylic resin on the second interlayer insulating film 110. The organic passivation film 111 has a function as a planarization film and is formed to have a thickness of about 2 μm. A through hole 112 is formed on the organic passivation film 111 to achieve conduction between the source electrode 108 and the pixel electrode 116.

[0054] A common electrode 113 is formed in a planar shape on the organic passivation film 111, a capacitor insulating film 114 is formed on the common electrode 113, and a pixel electrode 116 is formed on the capacitor insulating film 114. In order to achieve conduction between the pixel electrode 116 and the source electrode 108, a through hole 115 is formed in the through hole 112 of the organic passivation film 111 on the capacitor insulating film 114. An orientation film 117 for initially aligning liquid crystal molecules is formed in a manner covering the pixel electrode 116.

[0055] The counter substrate 200 is arranged opposite to the pixel electrode 116 and the like via the liquid crystal layer 300. A color filter 201 and a black matrix 202 are formed inside the counter substrate 200. The black matrix 202 covers the TFT and the through hole 112 to prevent light leakage. A protective film 203 is formed to cover the color filter 201 and the black matrix 202, and an alignment film 204 is formed thereon.

[0056] exist Figure 3 When a voltage is applied to the pixel electrode 116, electric lines of force are generated that pass through the liquid crystal layer 300, thereby rotating the liquid crystal molecules 301 and changing the light transmittance of the liquid crystal layer 300. By changing the light transmittance of the liquid crystal layer 300 for each pixel, an image is formed.

[0057] like Figure 3 As shown, the gate electrode 104 formed of metal faces the oxide semiconductor 106 via the gate insulating film 105. Since the gate electrode 104 is made of metal, it has the function of extracting oxygen from the oxide semiconductor 106 through the gate insulating film 105. As a result, the resistance of the oxide semiconductor 106 decreases, and the TFT no longer functions normally.

[0058] Fig.19 FIG. 1 is a cross-sectional view of a TFT as a comparative example. Fig.19 In FIG. 1 , the left side is a cross-sectional view of the vicinity of a TFT using an oxide semiconductor 106, and the right side is a capacitor wiring 120 and a capacitor electrode 122 formed simultaneously with the TFT to form a capacitor.

[0059] Fig.19 The layer structure is as Figure 3 As described in. Fig.19 and Figure 3 The difference is that a first gate insulating film 1051 formed of SiN and a second gate insulating film 1052 formed of SiO are present as the gate insulating film 105 between the gate electrode 104 and the oxide semiconductor film 106 . The SiO film 1052 is in contact with the oxide semiconductor film 106 .

[0060] Fig. 20 Yes means Fig.19 A cross-sectional view showing the effect of the first gate insulating film 1051 formed of SiN. The SiN film 1051 has the property of blocking oxygen. Fig. 20 In the embodiment, the gate electrode 104 formed of metal attracts oxygen from the SiO film and the oxide semiconductor film 106 as the second gate insulating film 1052. Fig. 20 As shown in FIG. 1 , the SiN film as the first gate insulating film 1051 blocks the movement of oxygen, thereby preventing oxygen from being released from the oxide semiconductor 106 . Fig. 20The × mark on the arrow in FIG. 1 indicates that oxygen is blocked by the SiN film 1051 .

[0061] Fig.21 Yes means Fig.19 The SiN film constituting the first gate insulating film 1051 blocks oxygen, but releases hydrogen. When the hydrogen reaches the oxide semiconductor film 106, the oxide semiconductor is reduced, that is, oxygen is taken away, causing the oxide semiconductor film 106 to be conductive.

[0062] Therefore, in Fig.19 Embodiments 1 to 4 described below avoid such a problem and provide a structure for coping with the phenomenon of oxygen being taken away from the oxide semiconductor layer 106 .

[0063] [Example 1]

[0064] Figure 4 This is a cross-sectional view showing the first aspect of Example 1. Figure 4 The layer structure and Figure 3 The structure is the same as described in. Figure 5 As shown, the gate electrode 104 has a structure in which an Al film 1042 is sandwiched between a Ti film as a base metal 1041 and a Ti film as a cap metal 1043 . Figure 4 and Figure 5 The feature of the present invention is that titanium nitride (TiN) is formed as a metal nitride film 10 on a gate electrode 104. A gate insulating film 105 made of a SiO film is formed on the titanium nitride film 10, and an oxide semiconductor film 106 is formed on the gate insulating film 106.

[0065] The titanium nitride film 10 is formed by sputtering, which can be performed continuously in the same chamber as the sputtering of the Ti film as the cap metal 1043. That is, after the Ti film 1043 is formed by sputtering, nitrogen gas is introduced to form the TiN film 10 by reactive sputtering.

[0066] exist Figure 5 In the embodiment, the base metal 1041 has a thickness of, for example, 50 nm, the Al film 1042 has a thickness of, for example, 300 nm, and the cap metal 1043 has a thickness of, for example, 50 nm. The TiN film 10 has a thickness of, for example, 10 nm, but may be about 5 nm to 30 nm. The gate insulating film 105 formed of SiO has a thickness of, for example, 300 nm to 500 nm, and the oxide semiconductor 106 has a thickness of, for example, 50 nm. Figure 5 The case of base metal 1041 in.

[0067] exist Figure 4In the embodiment, the titanium nitride film 10 formed on the gate electrode 104 can prevent oxygen from being absorbed from the oxide semiconductor 106 to the gate electrode 104. Therefore, it is possible to prevent the characteristics of the oxide semiconductor TFT from changing.

[0068] exist Figure 4 In the embodiment, the titanium nitride film 10 is not present on the entire upper surface of the gate electrode 104, but a vacancy exists as a region where a portion is not formed. The vacancy is used to form an intermediate resistance region (also referred to as an LDD region) 1062 in the oxide semiconductor film 106. That is, in the portion where the vacancy is formed, oxygen is extracted from the oxide semiconductor film 106 by the gate electrode 104, so that in this portion, the resistance of the oxide semiconductor 106 is reduced, forming the intermediate resistance region 1062. The intermediate resistance region 1062 suppresses the generation of hot carriers and stabilizes the characteristics of the oxide semiconductor TFT.

[0069] In addition, in the regions 1063 and 1064 where the drain electrode 107 or the source electrode 108 is stacked on the oxide semiconductor 106, oxygen is extracted from the oxide semiconductors 1063 and 1064 in large quantities by the drain electrode 107 or the source electrode 108, which is a metal, so that the oxide semiconductors 1063 and 1064 become conductive. On the other hand, the channel region 1061 of the oxide semiconductor maintains oxygen in the oxide semiconductor 1061 due to the presence of the titanium nitride film 10, so that high resistance is maintained, and the characteristics of the TFT can be maintained. Therefore, the reliability of the oxide semiconductor TFT can be maintained.

[0070] exist Figure 4 On the right side of the capacitor 104, the titanium nitride film 10 is also formed on the capacitor wiring 120 formed simultaneously with the gate electrode 104. However, since the titanium nitride film 10 has conductivity, the conduction between the capacitor wiring 120 and the capacitor electrode 122 is not impaired.

[0071] Figure 6 This is a cross-sectional view showing the second aspect of Example 1. Figure 6 and Figure 4 The difference is that the titanium nitride film 10 formed on the gate electrode 104 is formed only on a portion corresponding to the channel region 1061 of the oxide semiconductor 106. That is, in the channel region 1061 of the oxide semiconductor 106, oxygen extraction is blocked by the titanium nitride film 10, so that high resistance can be maintained.

[0072] However, since the gate electrode 104 deprives oxygen from the oxide semiconductor 106 corresponding to the portion other than the portion where the titanium nitride film 10 is formed on the gate electrode 104, the resistance of the oxide semiconductor 106 is reduced. In addition, the region of the oxide semiconductor 106 where the drain electrode 107 and the source electrode 108 are stacked, that is, the drain region 1063 and the source region 1064, has a significantly reduced resistance because a large amount of oxygen is extracted by the drain electrode 107 and the source electrode 108. In contrast, since oxygen is extracted only from the gate electrode 104 via the gate insulating film 105 between the channel region 1061 and the drain region 1063, or between the channel region 1061 and the source region 1064, the resistance value of the oxide semiconductor 106 is not significantly reduced compared with the drain region 1063 and the source region 1064. That is, in Figure 6 In the structure of , an intermediate resistance region (LDD region) is also formed. Figure 6 Also in the structure, it is possible to form an oxide semiconductor TFT with stable characteristics.

[0073] Figure 7 This is a cross-sectional view showing the third aspect of Example 1. Figure 7 As the first embodiment Figure 4 The difference is that the titanium nitride film 10 is also formed on the side surface of the gate electrode 104. Thus, it is possible to more effectively prevent the gate electrode 104 from absorbing oxygen from the oxide semiconductor 106.

[0074] In order to form the titanium nitride film 10 also on the side surface of the gate electrode 104, it is preferable that the taper of the side surface of the gate electrode 104 is not steep. For this purpose, the taper angle θ of the side surface of the gate electrode 104 is preferably 40 degrees to 60 degrees.

[0075] Figure 8 It is a cross-sectional view showing the fourth aspect of Example 1. Figure 8 As the second embodiment Figure 6 The difference is that the titanium nitride film 10 is also formed on the side surface of the gate electrode 104. Thus, absorption of oxygen from the oxide semiconductor 106 by the gate electrode 104 can be more effectively prevented. Figure 8 Other structures and Figure 6 and Figure 7 The structure is the same as described in .

[0076] In the above description, titanium nitride is used as an example of the metal nitride film 10, but the metal nitride film 10 is not limited thereto. For example, tantalum nitride (TaNx) or the like may also be used.

[0077] [Example 2]

[0078] The structure of the second embodiment is different from the structure of the first embodiment in that the substrate of the liquid crystal display device is not the polyimide substrate 100 but a glass substrate 90 . Fig. 9 This is a cross-sectional view showing the first aspect of Example 2. Fig. 9 Example 1 Figure 4 The difference is that there is no polyimide substrate and the first to third base films, but the gate electrode 104 is formed directly on the glass substrate 90.

[0079] Usually, alkali-free glass is used for the glass substrate 90. In addition, the influence of impurities from the glass substrate 90 on the oxide semiconductor 106 is prevented by the gate electrode 104 which is a metal. However, if the influence of impurities from the glass substrate 90 remains, as long as the gate electrode 104 is formed, the oxide semiconductor 106 can be prevented from being affected by the impurities from the glass substrate 90. Figure 3 The first to third base films 101, 102, 103 as described above are sufficient. Fig. 9 The other layers in the structure are due to Figure 4 The same, so the description is omitted.

[0080] Fig.10 This is a cross-sectional view showing the second aspect of Example 2. Fig.10 Example 1 Figure 6 The difference is that there is no polyimide substrate and the first to third base films, but the gate electrode 104 is formed directly on the glass substrate 90. Fig. 9 The same as described in , so it is omitted.

[0081] Fig.11 This is a cross-sectional view showing the third aspect of the second embodiment. Fig.11 Example 1 Figure 7 The difference is that there is no polyimide substrate and the first to third base films, but the gate electrode 104 is formed directly on the glass substrate 90. Fig. 9 The same as described in , so it is omitted.

[0082] Fig.12 This is a cross-sectional view showing the fourth aspect of the second embodiment. Fig.12 Example 1 Figure 8 The difference is that there is no polyimide substrate and the first to third base films, but the gate electrode 104 is formed directly on the glass substrate 90. Fig. 9 The same as described in , so it is omitted.

[0083] [Example 3]

[0084] Fig.13 It is a cross-sectional view showing the first aspect of Example 3. Fig.13 Example 1 Figure 4The difference is that a metal oxide film 20 is formed on the gate electrode 104 instead of a metal nitride film. The metal oxide film 20 can also prevent the gate electrode 104 from extracting oxygen from the oxide semiconductor 106. That is, the role of the metal oxide film 20 is the same as that of the embodiment 1. Figure 4 The effect is the same as described for the metal nitride film.

[0085] As the types of metal oxide 20, there are various oxide semiconductors described above, metal oxide conductors such as ITO, insulating metal oxides such as aluminum oxide (AlOx), etc. In addition, as other metal oxide conductors, there are AZO (Aluminum doped Zinc Oxide), IZO (Indium Zinc Oxide), etc. The film thickness of the metal oxide film 20 is preferably 5nm to 30nm, similar to the case of the metal nitride film.

[0086] Since metal oxides are also insulators, Fig.13 In the embodiment, a through hole is formed in the metal oxide film 20 formed on the capacitor wiring 120 at a portion where the capacitor wiring 120 and the capacitor electrode 122 are connected. Fig.13 The other structures and functions are the same as those of Example 1 Figure 4 The structure and function described in are the same, so they are omitted.

[0087] Fig.14 It is a cross-sectional view showing the second aspect of Example 3. Fig.14 Example 1 Figure 6 The difference is that a metal oxide film 20 is formed instead of a metal nitride film. Fig.14 The role of the metal oxide film 20 in Figure 6 The function of the metal nitride film 20 is the same as that of the metal nitride film 20, so the description is omitted.

[0088] Fig.15 2 is a cross-sectional view showing the third embodiment of the present invention. Fig.15 In the embodiment, the side surface of the gate electrode 104 is covered with the metal oxide film 20 . Fig.15 Example 1 Figure 7 The difference is that a metal oxide film 20 is formed instead of a metal nitride film. Fig.15 The role of the metal oxide film 20 in Figure 7 The function of the metal nitride film 20 is the same as that of the metal nitride film 20, so the description is omitted.

[0089] Fig.16 2 is a cross-sectional view showing the fourth embodiment of the third embodiment. Fig.16 In the embodiment, the side surface of the gate electrode 104 is covered with the metal oxide film 20 . Fig.16 Example 1 Figure 8The difference is that a metal oxide film 20 is formed instead of a metal nitride film. Fig.16 The role of the metal oxide film 20 in Figure 8 The function of the metal nitride film is the same as that of the metal nitride film, so the description is omitted.

[0090] [Example 4]

[0091] Fig.17 1 is a cross-sectional view showing the first embodiment of the fourth embodiment. Fig.17 In the embodiment, a metal oxide film 20 serving as an insulating film is formed on the gate electrode 104. As the metal oxide film 20 serving as the insulating film, for example, an aluminum oxide (AlOx) film can be cited. The thickness of the aluminum oxide (AlOx) film 30 is 5 nm to 30 nm, similarly to the metal nitride film in the first embodiment.

[0092] The function of the aluminum oxide (AlOx) film 30 is also the same as that of Example 1. Figure 4 or Figure 7 The aluminum oxide (AlOx) film 30 has the same function as the metal nitride film described in the above. Since the aluminum oxide (AlOx) film 30 is an insulating film, it can not only cover the gate electrode 104 or the capacitor wiring 120, but also cover the entire substrate. Therefore, the aluminum oxide (AlOx) film 30 can also have a function as a barrier film for blocking impurities from the glass substrate 90 or the polyimide substrate 100.

[0093] Fig.18 It is a cross-sectional view showing the second aspect of Example 4. Fig.18 Example 2 Fig.12 The difference is that an aluminum oxide (AlOx) film 30 is formed on the gate electrode 104 instead of a metal nitride film, and the aluminum oxide (AlOx) film 30 is formed not only on the gate electrode 104 and the capacitor wiring 120 but also on the entire surface of the substrate. The role of the aluminum oxide (AlOx) film 30 is similar to Fig.17 The functions described in etc. are the same and therefore omitted.

[0094] As described above, according to the present invention, it is possible to effectively prevent oxygen from disappearing from the oxide semiconductor film, and to form a stable oxide semiconductor TFT.

[0095] Furthermore, an example in which an oxide semiconductor is applied to a liquid crystal display device has been described above, but the present invention can also be applied to other display devices such as an organic EL display device, a two-dimensional optical sensor, and other devices using an oxide semiconductor.

[0096] Description of Reference Numerals

[0097] 10…Metal nitride film, 11…Scanning line, 12…Image signal line, 13…Pixel, 14…Display area, 15…Terminal area, 16…Sealing material, 17…Flexible wiring substrate, 20…Metal oxide, 30…Aluminum oxide (AlOx) film, 90…Glass substrate, 100…Polyimide substrate, 101…First base film, 102…Second base film, 103…Third base film, 104…Gate electrode, 105…Gate insulating film, 106…Oxide semiconductor film, 107…Drain electrode, 108…Source electrode, 109…First interlayer insulating film, 110…Second interlayer insulating film, 111…Organic passivation film, 112…Through hole, 113…Common electrode, 114…Capacitor insulating film, 115…Through hole, 116…Pixel electrode, 117… Orientation film, 120…capacitor wiring, 121…through hole, 122…capacitor electrode, 136…through hole, 150…lower electrode, 151…organic EL layer, 152…cathode, 153…protective layer, 154…adhesive material, 155…polarizer, 160…bank, 200…counter substrate, 201…color filter, 202…black matrix, 203…protective film, 204…orientation film, 300…liquid crystal layer, 301…liquid crystal molecules, 1041…base metal, 1042…Al film, 1043…cap metal, 1051…SiN film, 1052…SiO film, 1061…channel region, 1062…intermediate resistance region (LDD region), 1063…drain region, 1064…source region, 1161…pixel electrode slit.

Claims

1. A semiconductor device comprising a TFT, wherein a gate insulating film is formed on a gate electrode, and an oxide semiconductor film is formed on the gate insulating film, wherein the semiconductor device is characterized in that: The oxide semiconductor film has a channel region, a drain region, and a source region. A metal nitride film is formed on the upper surface of the gate electrode at a portion facing the channel region of the oxide semiconductor film in a plan view. The metal nitride film does not exist on a portion of the upper surface of the gate electrode, The oxide semiconductor film has an intermediate resistance region between the channel region and the drain region and between the channel region and the source region. The metal nitride film is not formed on a portion of the upper surface of the gate electrode corresponding to the intermediate resistance region of the oxide semiconductor film, and the metal nitride film is formed on a portion of the upper surface of the gate electrode corresponding to the drain region and the source region of the oxide semiconductor film.

2. The semiconductor device according to claim 1, It is characterized in that In a plan view, the metal nitride film does not exist in a portion of the upper surface of the gate electrode corresponding to the drain region and the source region of the oxide semiconductor film.

3. The semiconductor device according to claim 1, It is characterized in that The metal nitride film is also formed on the side surface of the gate electrode.

4. The semiconductor device according to claim 1, It is characterized in that The metal nitride film is titanium nitride (TiN).

5. The semiconductor device according to claim 1, It is characterized in that The gate electrode has a structure in which a Ti layer is formed on an Al layer.

6. A semiconductor device comprising a TFT, wherein a gate insulating film is formed on a gate electrode, and an oxide semiconductor film is formed on the gate insulating film, wherein the semiconductor device is characterized in that: The oxide semiconductor film has a channel region, a drain region, and a source region. A metal oxide film is formed on the upper surface of the gate electrode at a portion facing the channel region of the oxide semiconductor film in a plan view. The metal oxide film does not exist on a portion of the upper surface of the gate electrode, The oxide semiconductor film has an intermediate resistance region between the channel region and the drain region and between the channel region and the source region. The metal oxide film is not formed on a portion of the upper surface of the gate electrode corresponding to the intermediate resistance region of the oxide semiconductor film, and the metal oxide film is formed on a portion of the upper surface of the gate electrode corresponding to the drain region and the source region of the oxide semiconductor film.

7. The semiconductor device according to claim 6, It is characterized in that In a plan view, the metal oxide film does not exist in a portion of the upper surface of the gate electrode corresponding to the drain region and the source region of the oxide semiconductor film.

8. The semiconductor device according to claim 6, It is characterized in that The metal oxide film is also formed on the side surface of the gate electrode.

9. The semiconductor device according to claim 6, It is characterized in that The metal oxide film is a conductive metal oxide film.

10. The semiconductor device according to claim 6, It is characterized in that The metal oxide film is ITO.

11. The semiconductor device according to claim 6, It is characterized in that The metal oxide film is an oxide semiconductor film formed separately from the oxide semiconductor film.

12. A semiconductor device comprising a TFT, wherein a gate insulating film is formed on a gate electrode, and an oxide semiconductor film is formed on the gate insulating film, wherein the semiconductor device is characterized in that: The oxide semiconductor film has a channel region, a drain region, and a source region. An insulating metal oxide film is formed on the upper surface of the gate electrode at a portion facing the channel region of the oxide semiconductor film in a plan view. The insulating metal oxide film does not exist on a portion of the upper surface of the gate electrode, In a plan view, the insulating metal oxide film does not exist in a portion of the upper surface of the gate electrode corresponding to the drain region and the source region of the oxide semiconductor film.

13. The semiconductor device according to claim 12, It is characterized in that The oxide semiconductor film has an intermediate resistance region between the channel region and the drain region and between the channel region and the source region. The insulating metal oxide film is not formed on a portion of the upper surface of the gate electrode corresponding to the intermediate resistance region of the oxide semiconductor, and the insulating metal oxide film is formed on a portion of the upper surface of the gate electrode corresponding to the drain region and the source region of the oxide semiconductor film.

14. The semiconductor device according to claim 12, It is characterized in that The insulating metal oxide film is also formed on the side surfaces of the gate electrode.

15. The semiconductor device according to claim 12, It is characterized in that The insulating metal oxide film is an aluminum oxide (AlOx) film.

16. A semiconductor device comprising a TFT, wherein a gate insulating film is formed on a gate electrode, and an oxide semiconductor film is formed on the gate insulating film, wherein the semiconductor device is characterized in that: The oxide semiconductor film has a channel region, a drain region, and a source region. An insulating metal oxide film is formed on the upper surface of the gate electrode at a portion facing the channel region of the oxide semiconductor film in a plan view. The insulating metal oxide film does not exist on a portion of the upper surface of the gate electrode, The oxide semiconductor film has an intermediate resistance region between the channel region and the drain region and between the channel region and the source region. The insulating metal oxide film is not formed on a portion of the upper surface of the gate electrode corresponding to the intermediate resistance region of the oxide semiconductor, and the insulating metal oxide film is formed on a portion of the upper surface of the gate electrode corresponding to the drain region and the source region of the oxide semiconductor film.

17. The semiconductor device according to claim 16, It is characterized in that The insulating metal oxide film is also formed on the side surfaces of the gate electrode.

18. The semiconductor device according to claim 16, It is characterized in that The insulating metal oxide film is an aluminum oxide (AlOx) film.

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