Semiconductor device
A semiconductor device includes a base insulating film including silicon, an oxide semiconductor film over the base insulating film, a gate insulating film over the oxide semiconductor film, a gate electrode which is in contact with the gate insulating film and overlaps with at least the oxide semiconductor film, and a source electrode and a drain electrode electrically connected to the oxide semiconductor film. The oxide semiconductor film includes a region in which a concentration of silicon distributed from the interface with the base insulating film toward an inside of the oxide semiconductor film is lower than or equal to 1.0 at. %. A crystal portion is included at least in the region.
1. A semiconductor device comprising:
an insulating film including silicon;
an oxide semiconductor layer over the insulating film;
a gate insulating film over the oxide semiconductor layer;
a gate electrode over the gate insulating film;
a source electrode electrically connected to the oxide semiconductor layer; and
a drain electrode electrically connected to the oxide semiconductor layer,
wherein the oxide semiconductor layer comprises:
a first region in contact with the insulating film; and
a second region over the first region,
wherein a concentration of silicon distributed in the first region is lower than or equal to 1.0 at. %, and
wherein the first region includes a first crystal portion.
2. The semiconductor device according to claim 1 , wherein a thickness of the first region is less than or equal to 5 nm.
3. The semiconductor device according to claim 1 , wherein the insulating film further includes oxygen.
4. The semiconductor device according to claim 1 , wherein at least part of silicon in the insulating film is bonded to oxygen.
5. The semiconductor device according to claim 1 , wherein the oxide semiconductor layer comprises a second crystal portion in the second region.
6. The semiconductor device according to claim 5 , wherein a c-axis in at least one of the first crystal portion and the second crystal portion is aligned in a direction substantially parallel to a normal vector of a surface of the insulating film.
7. The semiconductor device according to claim 1 , wherein a silicon concentration of the first region is lower than or equal to 0.1 at. %.
8. The semiconductor device according to claim 1 , wherein a carbon concentration of the first region is lower than or equal to 1.0×10 20 atoms/cm 3 .
9. A semiconductor device comprising:
a base insulating film including silicon;
an oxide semiconductor film over the base insulating film;
a gate insulating film over the oxide semiconductor film;
a gate electrode overlapping with the oxide semiconductor film; and
a source electrode and a drain electrode electrically connected to the oxide semiconductor film,
wherein the oxide semiconductor film comprises a first region in which a concentration of silicon distributed from an interface with the base insulating film toward an inside of the oxide semiconductor film is lower than or equal to 1.0 at. %, and
wherein at least the first region comprises a first crystal portion.
10. The semiconductor device according to claim 9 , wherein the first region is formed to be in contact with the interface with the base insulating film and have a thickness less than or equal to 5 nm.
11. The semiconductor device according to claim 9 , wherein the base insulating film further includes oxygen.
12. The semiconductor device according to claim 9 , wherein at least part of silicon in the base insulating film is bonded to oxygen.
13. The semiconductor device according to claim 9 , wherein the oxide semiconductor film comprises a second crystal portion in a second region.
14. The semiconductor device according to claim 13 , wherein a c-axis in at least one of the first crystal portion and the second crystal portion is aligned in a direction substantially parallel to a normal vector of a surface of the base insulating film.
15. The semiconductor device according to claim 9 , wherein a silicon concentration of the first region is lower than or equal to 0.1 at. %.
16. The semiconductor device according to claim 9 , wherein a carbon concentration of the first region is lower than or equal to 1.0×10 20 atoms/cm 3 .