Semiconductor device
A transistor includes a multilayer film in which an oxide semiconductor film and an oxide film are stacked, a gate electrode, and a gate insulating film. The multilayer film overlaps with the gate electrode with the gate insulating film interposed therebetween. The multilayer film has a shape having a first angle between a bottom surface of the oxide semiconductor film and a side surface of the oxide semiconductor film and a second angle between a bottom surface of the oxide film and a side surface of the oxide film. The first angle is acute and smaller than the second angle. Further, a semiconductor device including such a transistor is manufactured.
1. A semiconductor device comprising:
a transistor, wherein the transistor comprises:
an oxide semiconductor film comprising a channel formation region;
an oxide film over the oxide semiconductor film;
a gate electrode; and
a gate insulating film between the oxide semiconductor film and the gate electrode,
wherein the oxide semiconductor film has an angle formed between a bottom surface of the oxide semiconductor film and a side surface of the oxide semiconductor film, the angle is greater than or equal to 10° and less than 90°, and
wherein each of the oxide film and the oxide semiconductor film comprises an In-M-Zn oxide (M is one selected from the group consisting of Al, Ga, Ge, Y, Zr, Sn, La, Ce, and Nd), and the oxide film has a lower atomic ratio of In to M than the oxide semiconductor film.
2. The semiconductor device according to claim 1 ,
wherein the oxide semiconductor film comprises a crystal part, and
wherein a c-axis of the crystal part is parallel to a normal vector of a surface of the oxide semiconductor film.
3. The semiconductor device according to claim 1 , wherein the In-M-Zn oxide comprised in the oxide semiconductor film is an In—Ga—Zn oxide.
4. The semiconductor device according to claim 1 , wherein the In-M-Zn oxide comprised in the oxide film is an In—Ga—Zn oxide.
5. The semiconductor device according to claim 1 , wherein the gate electrode is located under the oxide semiconductor film.
6. A display device comprising:
a transistor; and
an electroluminescent element electrically connected to the transistor,
wherein the transistor comprises:
an oxide semiconductor film comprising a channel formation region;
an oxide film over the oxide semiconductor film;
a gate electrode; and
a gate insulating film between the oxide semiconductor film and the gate electrode,
wherein the oxide semiconductor film has an angle formed between a bottom surface of the oxide semiconductor film and a side surface of the oxide semiconductor film, the angle is greater than or equal to 10° and less than 90°, and
wherein each of the oxide film and the oxide semiconductor film comprises an In-M-Zn oxide (M is one selected from the group consisting of Al, Ga, Ge, Y, Zr, Sn, La, Ce, and Nd), and the oxide film has a lower atomic ratio of In to M than the oxide semiconductor film.
7. The display device according to claim 6 ,
wherein the oxide semiconductor film comprises a crystal part, and
wherein a c-axis of the crystal part is parallel to a normal vector of a surface of the oxide semiconductor film.
8. The display device according to claim 6 , wherein the In-M-Zn oxide comprised in the oxide semiconductor film is an In—Ga—Zn oxide.
9. The display device according to claim 6 , wherein the In-M-Zn oxide comprised in the oxide film is an In—Ga—Zn oxide.
10. The display device according to claim 6 , wherein the gate electrode is located under the oxide semiconductor film.
11. A display device comprising:
a transistor; and
a liquid crystal element electrically connected to the transistor,
wherein the transistor comprises:
an oxide semiconductor film comprising a channel formation region;
an oxide film over the oxide semiconductor film;
a gate electrode; and
a gate insulating film between the oxide semiconductor film and the gate electrode,
wherein the oxide semiconductor film has an angle formed between a bottom surface of the oxide semiconductor film and a side surface of the oxide semiconductor film, the angle is greater than or equal to 10° and less than 90°, and
wherein each of the oxide film and the oxide semiconductor film comprises an In-M-Zn oxide (M is one selected from the group consisting of Al, Ga, Ge, Y, Zr, Sn, La, Ce, and Nd), and the oxide film has a lower atomic ratio of In to M than the oxide semiconductor film.
12. The display device according to claim 11 ,
wherein the oxide semiconductor film comprises a crystal part, and
wherein a c-axis of the crystal part is parallel to a normal vector of a surface of the oxide semiconductor film.
13. The display device according to claim 11 , wherein the In-M-Zn oxide comprised in the oxide semiconductor film is an In—Ga—Zn oxide.
14. The display device according to claim 11 , wherein the In-M-Zn oxide comprised in the oxide film is an In—Ga—Zn oxide.
15. The display device according to claim 11 , wherein the gate electrode is located under the oxide semiconductor film.