Semiconductor Device and Display Device Including the Same

Abstract

In a semiconductor device using a transistor including an oxide semiconductor, a change in electrical characteristics is inhibited and reliability is improved. The transistor includes a first gate electrode; a first insulating film over the first gate electrode; an oxide semiconductor film over the first insulating film; a source electrode electrically connected to the oxide semiconductor film; a drain electrode electrically connected to the oxide semiconductor film; a second insulating film over the oxide semiconductor film, the source electrode, and the drain electrode; and a second gate electrode over the second insulating film. The second insulating film includes oxygen. The second gate electrode includes the same metal element as at least one of metal elements of the oxide semiconductor film and has a region thinner than the oxide semiconductor film.

What is claimed is: 
     
         1 . A semiconductor device comprising a transistor, the transistor comprising:
 a first gate electrode;   a first insulating film over the first gate electrode;   an oxide semiconductor film over the first insulating film;   a source electrode electrically connected to the oxide semiconductor film;   a drain electrode electrically connected to the oxide semiconductor film;   a second insulating film over the oxide semiconductor film, the source electrode, and the drain electrode; and   a second gate electrode over the second insulating film,   wherein the second insulating filmhn includes oxygen, and   wherein the second gate electrode includes a same metal element as at least one of metal elements of the oxide semiconductor film and has a region thinner than the oxide semiconductor film.   
     
     
         2 . The semiconductor device according to  claim 1 , wherein the thickness of the second gate electrode is greater than or equal to 5 nm and less than or equal to 35 nm. 
     
     
         3 . The semiconductor device according to  claim 1 , wherein the oxide semiconductor film includes oxygen, In, Zn, and M (M is Ti, Ga, Sn, Y, Zr, La, Ce, Nd, or Hf). 
     
     
         4 . The semiconductor device according to  claim 1 , wherein the oxide semiconductor film includes a crystal part and the crystal part has c-axis alignment. 
     
     
         5 . A display device comprising a display element and the semiconductor device according to  claim 1 . 
     
     
         6 . A display module comprising a touch sensor and the display device according to  claim 5 . 
     
     
         7 . An electronic appliance comprising an operation key or a battery, and the display module according to  claim 6 . 
     
     
         8 . A semiconductor device comprising a transistor, the transistor comprising:
 a first gate electrode;   a first insulating film over the first gate electrode;   an oxide semiconductor film over the first insulating film;   a source electrode electrically connected to the oxide semiconductor film;   a drain electrode electrically connected to the oxide semiconductor film;   a second insulating film over the oxide semiconductor film, the source electrode, and the drain electrode; and   a second gate electrode over the second insulating film,   wherein the second gate electrode is electrically connected to the first gate electrode through an opening provided in the first insulating film and the second insulating film,   wherein the second insulating film includes oxygen, and   wherein the second gate electrode includes a same metal element as at least one of metal elements of the oxide semiconductor film and has a region thinner than the oxide semiconductor film.   
     
     
         9 . The semiconductor device according to  claim 8 , wherein the thickness of the second gate electrode is greater than or equal to 5 nm and less than or equal to 35 nm. 
     
     
         10 . The semiconductor device according to  claim 8 , wherein the oxide semiconductor film includes oxygen, In, Zn, and M (M is Ti, Ga, Sn, Y, Zr, La, Ce, Nd, or Hf). 
     
     
         11 . The semiconductor device according to  claim 8 , wherein the oxide semiconductor film includes a crystal part and the crystal part has c-axis alignment. 
     
     
         12 . A display device comprising a display element and the semiconductor device according to  claim 8 . 
     
     
         13 . A display module comprising a touch sensor and the display device according to  claim 12 . 
     
     
         14 . An electronic appliance comprising an operation key or a battery, and the display module according to  claim 13 . 
     
     
         15 . A semiconductor device comprising a transistor, the transistor comprising: a first gate electrode;
 a first insulating film over the first gate electrode;   an oxide semiconductor film over the first insulating film;   a second insulating film over the oxide semiconductor film;   a source electrode electrically connected to the oxide semiconductor film through an opening provided in the second insulating film;   a drain electrode electrically connected to the oxide semiconductor film through an opening provided in the second insulating film; and   a second gate electrode over the second insulating film,   wherein the second insulating film includes oxygen, and   wherein the second gate electrode includes a same metal element as at least one of metal elements of the oxide semiconductor film and has a region thinner than the oxide semiconductor film.   
     
     
         16 . The semiconductor device according to  claim 15 , wherein the thickness of the second gate electrode is greater than or equal to 5 nm and less than or equal to 35 nm. 
     
     
         17 . The semiconductor device according to  claim 15 , wherein the oxide semiconductor film includes oxygen, In, Zn, and M (M is Ti, Ga, Sn, Y, Zr, La, Ce, Nd, or Hf). 
     
     
         18 . The semiconductor device according to  claim 15 , wherein the oxide semiconductor film includes a crystal part and the crystal part has c-axis alignment. 
     
     
         19 . A display device comprising a display element and the semiconductor device according to  claim 15 . 
     
     
         20 . A display module comprising a touch sensor and the display device according to  claim 19 . 
     
     
         21 . An electronic appliance comprising an operation key or a battery, and the display module according to  claim 20 . 
     
     
         22 . A semiconductor device comprising a transistor, the transistor comprising:
 a first gate electrode;   a first insulating film over the first gate electrode;   an oxide semiconductor film over the first insulating film;   a second insulating film over the oxide semiconductor film;   a source electrode electrically connected to the oxide semiconductor film through an opening provided in the second insulating film;   a drain electrode electrically connected to the oxide semiconductor film through an opening provided in the second insulating film; and   a second gate electrode over the second insulating film,   wherein the second gate electrode is electrically connected to the first gate electrode through an opening provided in the first insulating film and the second insulating film,   wherein the second insulating film includes oxygen, and   wherein the second gate electrode includes a same metal element as at least one of metal elements of the oxide semiconductor film and has a region thinner than the oxide semiconductor film.   
     
     
         23 . The semiconductor device according to  claim 22 , wherein the thickness of the second gate electrode is greater than or equal to 5 nm and less than or equal to 35 nm. 
     
     
         24 . The semiconductor device according to  claim 22 , wherein the oxide semiconductor film includes oxygen, In, Zn, and M (M is Ti, Ga, Sn, Y, Zr, La, Ce, Nd, or Hf). 
     
     
         25 . The semiconductor device according to  claim 22 , wherein the oxide semiconductor film includes a crystal part and the crystal part has c-axis alignment. 
     
     
         26 . A display device comprising a display element and the semiconductor device according to  claim 22 . 
     
     
         27 . A display module comprising a touch sensor and the display device according to  claim 26 . 
     
     
         28 . An electronic appliance comprising an operation key or a battery, and the display module according to  claim 27 .