Semiconductor device
A semiconductor device is described, which includes a first transistor, a second transistor, and a capacitor. The second transistor and the capacitor are provided over the first transistor so as to overlap with a gate of the first transistor. A semiconductor layer of the second transistor and a dielectric layer of the capacitor are directly connected to the gate of the first transistor. The second transistor is a vertical transistor, where its channel direction is perpendicular to an upper surface of a semiconductor layer of the first transistor.
1. A semiconductor device comprising:
a first transistor comprising a first semiconductor layer; and
a second transistor being over and overlapping with the first transistor,
wherein a channel length direction between source and drain regions of the second transistor is perpendicular to an upper surface of the first semiconductor layer.
2. The semiconductor device according to claim 1 , further comprising a capacitor which is located over and overlaps with the first transistor.
3. The semiconductor device according to claim 1 , wherein a channel in the first semiconductor layer overlaps with the channel of the second transistor.
4. The semiconductor device according to claim 1 , wherein the first transistor is located over an insulating surface.
5. The semiconductor device according to claim 1 ,
wherein the first transistor further comprises:
a first insulating layer over the first semiconductor layer; and
a first electrode layer over the first insulating layer, and
wherein the second transistor comprises:
a second semiconductor layer in direct contact with the first electrode layer;
a second insulating layer adjacent to a side surface of the second semiconductor layer;
a second electrode layer adjacent to the side surface of the second semiconductor layer with the second insulating layer therebetween; and
a third electrode layer over the second semiconductor layer.
6. The semiconductor device according to claim 5 , wherein the second electrode layer is located between the first electrode layer and the third electrode layer.
7. The semiconductor device according to claim 5 ,
wherein the second semiconductor layer comprises an oxide semiconductor, and
wherein the first semiconductor layer comprises a material selected from single crystalline silicon, amorphous silicon, and polycrystalline silicon.
8. The semiconductor device according to claim 5 , further comprising a capacitor which comprises:
a dielectric layer in direct contact with the first electrode layer; and
a fourth electrode layer over the dielectric layer.
9. The semiconductor device according to claim 8 , wherein the second semiconductor layer and the dielectric layer exist in the same layer.
10. The semiconductor device according to claim 8 , wherein the second insulating layer and the dielectric layer exist in the same layer.
11. The semiconductor device according to claim 8 , wherein the second insulating layer and the second electrode layer surround the second semiconductor layer.
12. An electronic device comprising the semiconductor device according to claim 1 .
13. A semiconductor device comprising:
a first semiconductor layer;
a first insulating layer over the first semiconductor layer;
a first electrode layer over the first insulating layer;
a second semiconductor layer over and in direct contact with the first electrode layer;
a second insulating layer adjacent to a side surface of the second semiconductor layer;
a second electrode layer adjacent to the side surface of the second semiconductor layer with the second insulating layer therebetween; and
a third electrode layer over and in direct contact with the second semiconductor layer.
14. The semiconductor device according to claim 13 , wherein a channel in the first semiconductor layer overlaps with a channel in the second semiconductor layer.
15. The semiconductor device according to claim 13 , wherein the second electrode layer is located between the first electrode layer and the third electrode layer.
16. The semiconductor device according to claim 13 , wherein the first semiconductor layer is located over an insulating surface.
17. The semiconductor device according to claim 13 , wherein the second insulating layer and the second electrode layer surround the second semiconductor layer.
18. The semiconductor device according to claim 13 ,
wherein the second semiconductor layer comprises an oxide semiconductor, and
wherein the first semiconductor layer comprises a material selected from single crystalline silicon, amorphous silicon, and polycrystalline silicon.
19. The semiconductor device according to claim 13 , further comprising:
a dielectric layer over and in direct contact with the first electrode layer; and
a fourth electrode layer over the dielectric layer.
20. The semiconductor device according to claim 19 , wherein the second semiconductor layer and the dielectric layer exist in the same layer.
21. The semiconductor device according to claim 19 , wherein the second insulating layer and the dielectric layer exist in the same layer.
22. An electronic device comprising the semiconductor device according to claim 13 .