Oxide material and semiconductor device
An object is to provide a material suitably used for a semiconductor included in a transistor, a diode, or the like. Another object is to provide a semiconductor device including a transistor in which the condition of an electron state at an interface between an oxide semiconductor film and a gate insulating film in contact with the oxide semiconductor film is favorable. Further, another object is to manufacture a highly reliable semiconductor device by giving stable electric characteristics to a transistor in which an oxide semiconductor film is used for a channel. A semiconductor device is formed using an oxide material which includes crystal with c-axis alignment, which has a triangular or hexagonal atomic arrangement when seen from the direction of a surface or an interface and rotates around the c-axis.
1. A semiconductor device comprising:
a gate electrode;
an insulating layer over the gate electrode;
an oxide semiconductor layer over the insulating layer, the oxide semiconductor layer comprising a stack of a first film and a second film,
wherein the second film is positioned over the first film,
wherein one of the first film and the second film comprises an In—Sn—Ga—Zn—O-based oxide semiconductor film,
wherein each of the first film and the second film comprises a crystal,
wherein one of the first film and the second film comprises a c-axis aligned crystals, and
wherein the c-axis aligned crystals in the second film have different a-axis directions and b-axis directions from each other.
2. The semiconductor device according to claim 1 , wherein the first film and the second film have a different composition from each other.
3. The semiconductor device according to claim 1 ,
wherein the insulating layer is in contact with the oxide semiconductor layer, and
wherein the insulating layer comprises silicon and oxygen.
4. The semiconductor device according to claim 1 ,
wherein the insulating layer is in contact with the first film, and
wherein the insulating layer comprises silicon and oxygen.
5. The semiconductor device according to claim 1 , further comprising:
a source electrode and a drain electrode each in contact with the oxide semiconductor layer,
wherein one of the source electrode and the drain electrode is electrically connected to a display element.
6. The semiconductor device according to claim 5 , wherein the display element is a liquid crystal element.
7. A semiconductor device comprising:
a gate electrode;
an insulating layer over the gate electrode;
an oxide semiconductor layer over the insulating layer, the oxide semiconductor layer comprising a stack of a first film and a second film,
wherein the second film is positioned over the first film,
wherein one of the first film and the second film comprises an In—Sn—Ga—Zn—O-based oxide semiconductor film,
wherein each of the first film and the second film comprises a crystal,
wherein the second film comprises a c-axis aligned crystals, and
wherein the c-axis aligned crystals in the second film have different a-axis directions and b-axis directions from each other.
8. The semiconductor device according to claim 7 , wherein the first film and the second film have a different composition from each other.
9. The semiconductor device according to claim 7 ,
wherein the insulating layer is in contact with the oxide semiconductor layer, and
wherein the insulating layer comprises silicon and oxygen.
10. The semiconductor device according to claim 7 ,
wherein the insulating layer is in contact with the first film, and
wherein the insulating layer comprises silicon and oxygen.
11. The semiconductor device according to claim 7 , further comprising:
a source electrode and a drain electrode each in contact with the oxide semiconductor layer,
wherein one of the source electrode and the drain electrode is electrically connected to a display element.
12. The semiconductor device according to claim 11 , wherein the display element is a liquid crystal element.