Liquid crystal display device

Abstract

The present invention provides a method for fabricating a transistor in a semiconductor device using an oxide semiconductor film that has stable electrical characteristics and low signal delay due to wiring resistance, a semiconductor device having said transistor, and a high-performance display device. [Solution] As a method for manufacturing source electrodes and drain electrodes that come into contact with an oxide semiconductor film, first metal films 110a, 112a and second metal films 110b, 112b are formed, a first photolithography process is performed on the second metal film, and a portion of the second metal film is removed by first etching. Subsequently, third metal films 110c, 112c are formed on the first and second metal films, a second photolithography process is performed on the third metal film, and a portion of the first and third metal films is removed by second etching. The second etching removes the first and third metal films outside the edge of the second metal film removed by the first etching.

Claims

1. A liquid crystal display device having transistors in the pixel portion, A first conductive film having the function of a photoelectrode of the transistor, A first insulating film having a region positioned above the first conductive film, An oxide semiconductor film having a region positioned above the first insulating film and having a channel formation region for the transistor, A first film having a region positioned above the oxide semiconductor film, a region in contact with the oxide semiconductor film, and containing one of tungsten, tantalum, titanium, and molybdenum, A second film having a region in contact with the upper surface of the first film and containing copper, A third film having a region in contact with the upper surface and side surface of the second film, a region in contact with the upper surface of the first film, and containing a metal, A second insulating film having a region positioned above the first film, a region positioned above the second film, a region positioned above the third film, and a region in contact with the oxide semiconductor film, The third film does not have a region in contact with the oxide semiconductor film. The oxide semiconductor film comprises a first oxide semiconductor film and a second oxide semiconductor film having a region positioned above the first oxide semiconductor film. Each of the first oxide semiconductor film and the second oxide semiconductor film comprises In, Ga, and Zn. The second oxide semiconductor film has c-axis oriented crystalline portions, The second oxide semiconductor film has a high atomic ratio of Ga to In. LCD display device.

2. A liquid crystal display device having transistors in the pixel portion, A first conductive film having the function of a photoelectrode of the transistor, A first insulating film having a region positioned above the first conductive film, An oxide semiconductor film having a region positioned above the first insulating film and having a channel formation region for the transistor, A first film having a region positioned above the oxide semiconductor film, a region in contact with the oxide semiconductor film, and containing one of tungsten, tantalum, titanium, and molybdenum, A second film having a region in contact with the upper surface of the first film and containing copper, A third film having a region in contact with the upper surface and side surface of the second film, a region in contact with the upper surface of the first film, and containing a metal, A second insulating film having a region positioned above the first film, a region positioned above the second film, a region positioned above the third film, and a region in contact with the oxide semiconductor film, The first insulating film comprises a first layer containing nitrogen and silicon, and a second layer having a region located above the first layer and containing oxygen and silicon. The third film does not have a region in contact with the oxide semiconductor film. The oxide semiconductor film comprises a first oxide semiconductor film and a second oxide semiconductor film having a region positioned above the first oxide semiconductor film. Each of the first oxide semiconductor film and the second oxide semiconductor film comprises In, Ga, and Zn. The second oxide semiconductor film has c-axis oriented crystalline portions, The second oxide semiconductor film has a high atomic ratio of Ga to In. LCD display device.

3. In claim 1 or claim 2, The third film has the function of suppressing the diffusion of copper elements from the second film. LCD display device.

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