Oxide semiconductor film and semiconductor device
To provide an oxide semiconductor film having stable electric conductivity and a highly reliable semiconductor device having stable electric characteristics by using the oxide semiconductor film. The oxide semiconductor film contains indium (In), gallium (Ga), and zinc (Zn) and includes a c-axis-aligned crystalline region aligned in the direction parallel to a normal vector of a surface where the oxide semiconductor film is formed. Further, the composition of the c-axis-aligned crystalline region is represented by In 1+δ Ga 1-δ O 3 (ZnO) m (0<δ<1 and m=1 to 3 are satisfied), and the composition of the entire oxide semiconductor film including the c-axis-aligned crystalline region is represented by In x Ga y O 3 (ZnO) m (0<x<2, 0<y<2, and m=1 to 3 are satisfied).
1. A semiconductor device comprising:
a substrate;
a source electrode and a drain electrode over the substrate; and
a semiconductor film between the source electrode and the drain electrode, the semiconductor film comprising a first region and a second region over the first region,
wherein a material of the semiconductor film is an In—Ga—Zn—O-based metal oxide, and
wherein the In—Ga—Zn—O-based metal oxide in the first region has a different composition ratio of In to Ga and Zn from the In—Ga—Zn—O-based metal oxide in the second region.
2. The semiconductor device according to claim 1 , further comprising a gate electrode between the substrate and the semiconductor film.
3. The semiconductor device according to claim 1 , further comprising a gate electrode over the semiconductor film.
4. The semiconductor device according to claim 1 ,
wherein a composition of the first region is represented by In 1+δ Ga 1-δ O 3 (ZnO) m , and
wherein 0<δ<1 and m=1 to 3 are satisfied.
5. The semiconductor device according to claim 1 , wherein the second region has a higher concentration of Zn than the first region.
6. The semiconductor device according to claim 1 ,
wherein the second region comprises crystals, and
wherein an alignment of c-axes of the crystals in the second region is higher than an alignment of each of a-axes and b-axes of the crystals in the second region.
7. The semiconductor device according to claim 1 , wherein crystallinity of atoms in the second region is higher than crystallinity of atoms in the first region.
8. An electronic appliance comprising the semiconductor device according to claim 1 , wherein the electronic appliance is any one of a television set, a monitor, a camera, a video camera, a digital photo frame, a mobile phone handset, a game machine, an information terminal, an audio reproducing device and a display device.
9. A semiconductor device comprising:
a substrate;
a source electrode and a drain electrode over the substrate;
a first semiconductor film between the source electrode and the drain electrode; and
a second semiconductor film over the first semiconductor film, the second semiconductor film comprising a first region and a second region over the first region,
wherein a material of the second semiconductor film is an In—Ga—Zn—O-based metal oxide, and
wherein the In—Ga—Zn—O-based metal oxide in the first region has a different composition ratio of In to Ga and Zn from the In—Ga—Zn—O-based metal oxide in the second region.
10. The semiconductor device according to claim 9 , further comprising a gate electrode between the substrate and the first semiconductor film.
11. The semiconductor device according to claim 9 , further comprising a gate electrode over the second semiconductor film.
12. The semiconductor device according to claim 9 , wherein the second region has a higher concentration of Zn than the first region.
13. The semiconductor device according to claim 9 ,
wherein the second region comprises crystals, and
wherein an alignment of c-axes of the crystals in the second region is higher than an alignment of each of a-axes and b-axes of the crystals in the second region.
14. The semiconductor device according to claim 9 , wherein crystallinity of atoms in the second region is higher than crystallinity of atoms in the first region.
15. The semiconductor device according to claim 9 ,
wherein the first semiconductor film comprises a third region and a fourth region over the third region,
wherein the fourth region comprises crystals, and
wherein an alignment of c-axes of the crystals in the fourth region is higher than an alignment of each of a-axes and b-axes of the crystals in the fourth region.