Semiconductor device
An embodiment is a semiconductor device which includes a first oxide semiconductor layer over a substrate having an insulating surface and including a crystalline region formed by growth from a surface of the first oxide semiconductor layer toward an inside; a second oxide semiconductor layer over the first oxide semiconductor layer; a source electrode layer and a drain electrode layer which are in contact with the second oxide semiconductor layer; a gate insulating layer covering the second oxide semiconductor layer, the source electrode layer, and the drain electrode layer; and a gate electrode layer over the gate insulating layer and in a region overlapping with the second oxide semiconductor layer. The second oxide semiconductor layer is a layer including a crystal formed by growth from the crystalline region.
1. A semiconductor device comprising:
a transistor comprising:
a first gate;
a first gate insulating film over the first gate;
an oxide semiconductor film over the first gate insulating film;
a second gate insulating film over the oxide semiconductor film; and
a second gate over the second gate insulating film,
wherein the oxide semiconductor film comprises indium and zinc,
wherein the oxide semiconductor film comprises a crystalline region,
wherein a c-axis of the crystalline region is aligned in a direction perpendicular or substantially perpendicular to a surface of the oxide semiconductor film,
wherein the crystalline region comprises:
a first layer comprising indium; and
a second layer comprises gallium and does not comprise indium, and
wherein the first layer and the second layer are stacked in a direction along the c-axis of the crystalline region.
2. The semiconductor device according to claim 1 , comprising a source and a drain over and electrically connected to the oxide semiconductor film.
3. The semiconductor device according to claim 2 , wherein the second gate insulating film is located over the source and the drain.
4. The semiconductor device according to claim 2 , wherein the second gate overlaps the source and the drain.
5. The semiconductor device according to claim 1 , wherein the oxide semiconductor film comprises gallium.
6. The semiconductor device according to claim 1 , wherein a carrier density of the oxide semiconductor film is lower than 1.0×10 12 cm −3 .
7. The semiconductor device according to claim 1 , wherein the crystalline region comprises polycrystal.
8. The semiconductor device according to claim 1 , wherein the oxide semiconductor film is intrinsic or substantially intrinsic.
9. The semiconductor device according to claim 1 , wherein the oxide semiconductor film comprises hydrogen in a concentration of 5×10 19 cm −3 or lower.
10. A semiconductor device comprising:
a transistor comprising:
a gate;
a gate insulating film over the gate; and
an oxide semiconductor film over the gate insulating film;
wherein the oxide semiconductor film comprises indium and zinc,
wherein the oxide semiconductor film comprises a crystalline region,
wherein a c-axis of the crystalline region is aligned in a direction perpendicular or substantially perpendicular to a surface of the oxide semiconductor film,
wherein the crystalline region comprises:
a first layer comprising indium; and
a second layer comprises gallium and does not comprise indium, and
wherein the first layer and the second layer are stacked in a direction along the c-axis of the crystalline region.
11. The semiconductor device according to claim 10 , comprising a source and a drain over and electrically connected to the oxide semiconductor film.
12. The semiconductor device according to claim 11 , wherein the gate overlaps the source and the drain.
13. The semiconductor device according to claim 10 , wherein the oxide semiconductor film comprises gallium.
14. The semiconductor device according to claim 10 , wherein a carrier density of the oxide semiconductor film is lower than 1.0×10 12 cm −3 .
15. The semiconductor device according to claim 10 , wherein the crystalline region comprises polycrystal.
16. The semiconductor device according to claim 10 , wherein the oxide semiconductor film is intrinsic or substantially intrinsic.
17. The semiconductor device according to claim 10 , wherein the oxide semiconductor film comprises hydrogen in a concentration of 5×10 19 cm −3 or lower.
18. A semiconductor device comprising:
a transistor comprising:
an oxide semiconductor film;
a gate insulating film over the oxide semiconductor film; and
a gate over the gate insulating film,
wherein the oxide semiconductor film comprises indium and zinc,
wherein the oxide semiconductor film comprises a crystalline region,
wherein a c-axis of the crystalline region is aligned in a direction perpendicular or substantially perpendicular to a surface of the oxide semiconductor film,
wherein the crystalline region comprises:
a first layer comprising indium; and
a second layer comprises gallium and does not comprise indium, and
wherein the first layer and the second layer are stacked in a direction along the c-axis of the crystalline region.
19. The semiconductor device according to claim 18 , comprising a source and a drain over and electrically connected to the oxide semiconductor film.
20. The semiconductor device according to claim 19 , wherein the gate insulating film is located over the source and the drain.
21. The semiconductor device according to claim 19 , wherein the gate overlaps the source and the drain.
22. The semiconductor device according to claim 18 , wherein the oxide semiconductor film comprises gallium.
23. The semiconductor device according to claim 18 , wherein a carrier density of the oxide semiconductor film is lower than 1.0×10 12 cm −3 .
24. The semiconductor device according to claim 18 , wherein the crystalline region comprises polycrystal.
25. The semiconductor device according to claim 18 , wherein the oxide semiconductor film is intrinsic or substantially intrinsic.
26. The semiconductor device according to claim 18 , wherein the oxide semiconductor film comprises hydrogen in a concentration of 5×10 19 cm −3 or lower.