Thin film transistor having oxide semiconductor layer
View Patent ↗Oxide layers which contain at least one metal element that is the same as that contained in an oxide semiconductor layer including a channel are formed in contact with the top surface and the bottom surface of the oxide semiconductor layer, whereby an interface state is not likely to be generated at each of an upper interface and a lower interface of the oxide semiconductor layer. Further, it is preferable that an oxide layer, which is formed using a material and a method similar to those of the oxide layers be formed over the oxide layers Accordingly, the interface state hardly influences the movement of electrons.
1. A semiconductor device comprising:
an oxide semiconductor layer over a first oxide layer;
a second oxide layer over the oxide semiconductor layer;
a first electrode and a second electrode in contact with the second oxide layer;
a third oxide layer in contact with the oxide semiconductor layer and over the first electrode and the second electrode;
an insulating layer over the third oxide layer; and
a third electrode over the insulating layer,
wherein the first oxide layer comprises at least one metal element contained in the oxide semiconductor layer.
2. The semiconductor device according to claim 1 , wherein the second oxide layer and the third oxide layer comprise the one metal element.
3. The semiconductor device according to claim 1 , wherein the one metal element is indium.
4. The semiconductor device according to claim 1 , wherein the oxide semiconductor layer contains indium, gallium, and zinc.
5. The semiconductor device according to claim 1 , wherein a side surface of the first oxide layer and a side surface of the second oxide layer are in contact with the third oxide layer.
6. The semiconductor device according to claim 1 , wherein the first oxide layer and the second oxide layer each have a smaller electron affinity than the oxide semiconductor layer.
7. The semiconductor device according to claim 1 , wherein the third oxide layer has a smaller electron affinity than the second oxide layer.
8. A semiconductor device comprising:
a stack including a first oxide layer, a second oxide layer, and an oxide semiconductor layer between the first oxide layer and the second oxide layer;
a source electrode and a drain electrode;
a third oxide layer;
a gate insulating layer; and
a gate electrode,
wherein the source electrode and the drain electrode are over and in contact with the stack,
wherein the third oxide layer is over the source electrode and the drain electrode and in contact with the oxide semiconductor layer,
wherein the gate insulating layer is positioned between the gate electrode and the stack, and
wherein the first oxide layer comprises at least one metal element contained in the oxide semiconductor layer.
9. The semiconductor device according to claim 8 , wherein the second oxide layer and the third oxide layer comprise the one metal element.
10. The semiconductor device according to claim 8 , wherein the one metal element is indium.
11. The semiconductor device according to claim 8 , wherein the oxide semiconductor layer contains indium, gallium, and zinc.
12. The semiconductor device according to claim 8 , wherein a side surface of the first oxide layer and a side surface of the second oxide layer are in contact with the third oxide layer.
13. The semiconductor device according to claim 8 , wherein the first oxide layer and the second oxide layer each have a smaller electron affinity than the oxide semiconductor layer.
14. The semiconductor device according to claim 8 , wherein the third oxide layer has a smaller electron affinity than the second oxide layer.
15. A semiconductor device comprising:
an oxide semiconductor layer over a first oxide layer;
a second oxide layer over the oxide semiconductor layer;
a first electrode and a second electrode in contact with the second oxide layer; and
a third oxide layer in contact with the oxide semiconductor layer and over the first electrode and the second electrode,
wherein the first oxide layer comprises at least one metal element contained in the oxide semiconductor layer.
16. The semiconductor device according to claim 15 , wherein the second oxide layer and the third oxide layer comprise the one metal element.
17. The semiconductor device according to claim 15 , wherein the one metal element is indium.
18. The semiconductor device according to claim 15 , wherein the oxide semiconductor layer contains indium, gallium, and zinc.
19. The semiconductor device according to claim 15 , wherein a side surface of the first oxide layer and a side surface of the second oxide layer are in contact with the third oxide layer.
20. The semiconductor device according to claim 15 , wherein the first oxide layer and the second oxide layer each have a smaller electron affinity than the oxide semiconductor layer.
21. The semiconductor device according to claim 15 , wherein the third oxide layer has a smaller electron affinity than the second oxide layer.