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 comprising silicon;
an oxide semiconductor film over the insulating film;
a gate insulating film over the oxide semiconductor film;
a gate electrode over the gate insulating film;
a source electrode electrically connected to the oxide semiconductor film; and
a drain electrode electrically connected to the oxide semiconductor film,
wherein the oxide semiconductor film comprises:
a first region in contact with the insulating film; and
a second region over the first region,
wherein a concentration of silicon in the first region is lower than or equal to 1.0 at. %,
wherein the first region comprises a crystal portion, and
wherein a c-axis in the crystal portion is aligned in a direction substantially parallel to a normal vector of a surface of the insulating film.
2. The semiconductor device according to claim 1 , wherein the insulating film further comprises oxygen.
3. The semiconductor device according to claim 1 , wherein the oxide semiconductor film comprises a second crystal portion in the second region.
4. The semiconductor device according to claim 1 , wherein an average surface roughness of the surface of the insulating film is less than or equal to 0.15 nm.
5. The semiconductor device according to claim 1 , wherein an end portion of the oxide semiconductor film is tapered at an angle of 20° to 50°.
6. The semiconductor device according to claim 1 , wherein the concentration of silicon in the first region is lower than or equal to 0.1 at. %.
7. A semiconductor device comprising:
an insulating film comprising silicon;
an oxide semiconductor film over the insulating film;
a gate insulating film over the oxide semiconductor film;
a gate electrode over the gate insulating film;
a source electrode electrically connected to the oxide semiconductor film; and
a drain electrode electrically connected to the oxide semiconductor film,
wherein the oxide semiconductor film comprises:
a first region in contact with the insulating film; and
a second region over the first region,
wherein a concentration of silicon in the first region is lower than or equal to 1.0 at. %,
wherein the first region comprises a crystal portion,
wherein a c-axis in the crystal portion is aligned in a direction substantially parallel to a normal vector of a surface of the insulating film, and
wherein a concentration of carbon in the first region is lower than or equal to 1.0×10 20 atoms/cm 3 .
8. The semiconductor device according to claim 7 , wherein the insulating film further comprises oxygen.
9. The semiconductor device according to claim 7 , wherein the oxide semiconductor film comprises a second crystal portion in the second region.
10. The semiconductor device according to claim 7 , wherein an average surface roughness of the surface of the insulating film is less than or equal to 0.15 nm.
11. The semiconductor device according to claim 7 , wherein an end portion of the oxide semiconductor film is tapered at an angle of 20° to 50°.
12. The semiconductor device according to claim 7 , wherein the concentration of silicon in the first region is lower than or equal to 0.1 at. %.
13. A semiconductor device comprising:
an insulating film comprising silicon;
an oxide semiconductor film over the insulating film;
a gate insulating film over the oxide semiconductor film;
a gate electrode over the gate insulating film;
a source electrode electrically connected to the oxide semiconductor film; and
a drain electrode electrically connected to the oxide semiconductor film,
wherein the oxide semiconductor film comprises:
a first region in contact with the insulating film; and
a second region over the first region,
wherein a concentration of silicon in the first region is lower than or equal to 1.0 at. %,
wherein the first region comprises a crystal portion,
wherein a c-axis in the crystal portion is aligned in a direction substantially parallel to a normal vector of a surface of the insulating film,
wherein a concentration of carbon in the first region is lower than or equal to 1.0×10 20 atoms/cm 3 , and
wherein a thickness of the first region is less than or equal to 5 nm.
14. The semiconductor device according to claim 13 , wherein the insulating film further comprises oxygen.
15. The semiconductor device according to claim 13 , wherein the oxide semiconductor film comprises a second crystal portion in the second region.
16. The semiconductor device according to claim 13 , wherein an average surface roughness of the surface of the insulating film is less than or equal to 0.15 nm.
17. The semiconductor device according to claim 13 , wherein an end portion of the oxide semiconductor film is tapered at an angle of 20° to 50°.
18. The semiconductor device according to claim 13 , wherein the concentration of silicon in the first region is lower than or equal to 0.1 at. %.