Semiconductor device
View Patent ↗A transistor used for a semiconductor device for high power application needs to have a channel region for obtaining higher drain current. As an example of such a transistor, a vertical (trench type) transistor has been considered; however, the vertical transistor cannot have a high on/off ratio of drain current and thus cannot have favorable transistor characteristics. Over a substrate having conductivity, an oxide semiconductor layer having a surface having a dotted pattern of a plurality of island-shaped regions with a tapered shape in a cross section is sandwiched between a first electrode formed between the substrate and the oxide semiconductor layer and a second electrode formed over the oxide semiconductor layer, and a conductive layer functioning as a gate electrode is formed on the side surface of the island-shaped region in the oxide semiconductor layer with an insulating layer provided therebetween.
1. A semiconductor device comprising:
a metal substrate;
a first electrode over the metal substrate;
an oxide semiconductor layer over the first electrode, the oxide semiconductor layer comprising a first island-shaped region and a second island-shaped region adjacent to the first island-shaped region;
a second electrode over a top surface of the first island-shaped region;
a third electrode over a top surface of the second island-shaped region;
a first insulating layer over the oxide semiconductor layer, the second electrode and the third electrode;
a gate electrode over a side surface of the first island-shaped region and a side surface of the second island-shaped region, wherein the first insulating layer is located between the gate electrode and the first island-shaped region and between the gate electrode and the second island-shaped region;
a second insulating layer over the first insulating layer and the gate electrode; and
a conductive layer over the first insulating layer and the second insulating layer, the conductive layer electrically connected to the second electrode and the third electrode.
2. The semiconductor device according to claim 1 , wherein the gate electrode is located between the first island-shaped region and the second island-shaped region.
3. The semiconductor device according to claim 1 , wherein the second electrode includes an oxide semiconductor layer including phosphorus or boron.
4. The semiconductor device according to claim 1 , wherein the first electrode includes tungsten.
5. The semiconductor device according to claim 1 , wherein each of the first island-shaped region and the second island-shaped region has a tapered shape.
6. The semiconductor device according to claim 1 , further comprising a second conductive layer between the first electrode and the oxide semiconductor layer.
7. The semiconductor device according to claim 1 , wherein the second electrode is overlapped with the second insulating layer with the first insulating layer located therebetween.
8. The semiconductor device according to claim 1 ,
wherein the oxide semiconductor layer has depression between the first island-shaped region and the second island-shaped region, and
wherein the first insulating layer is in contact with a surface of the depression.
9. The semiconductor device according to claim 1 ,
wherein the conductive layer passes through a first opening in the gate electrode so as to be electrically connected to the second electrode, and
wherein the conductive layer passes through a second opening in the gate electrode so as to be electrically connected to the third electrode.
10. The semiconductor device according to claim 1 , wherein the oxide semiconductor layer comprises a crystal part, a direction of c-axis of the crystal part is substantially parallel to a normal vector of a surface of the oxide semiconductor layer.
11. A semiconductor device comprising:
a first electrode;
an oxide semiconductor layer over the first electrode, the oxide semiconductor layer comprises a first island-shaped region and a second island-shaped region adjacent to the first island-shaped region;
a second electrode over a top surface of the first island-shaped region;
a third electrode over a top surface of the second island-shaped region;
an insulating layer over the oxide semiconductor layer, the second electrode and the third electrode; and
a gate electrode over a side surface of the first island-shaped region and a side surface of the second island-shaped region, wherein the insulating layer is located between the gate electrode and the first island-shaped region and between the gate electrode and the second island-shaped region; and
a conductive layer over the insulating layer, the conductive layer electrically connected to the second electrode and the third electrode.
12. The semiconductor device according to claim 11 , wherein the gate electrode is located between the first island-shaped region and the second island-shaped region.
13. The semiconductor device according to claim 11 , wherein the second electrode includes an oxide semiconductor layer including phosphorus or boron.
14. The semiconductor device according to claim 11 , wherein the first electrode includes tungsten.
15. The semiconductor device according to claim 11 , wherein each of the first island-shaped region and the second island-shaped region has a tapered shape.
16. The semiconductor device according to claim 11 , further comprising a second conductive layer between the first electrode and the oxide semiconductor layer.
17. The semiconductor device according to claim 11 , wherein the gate electrode and the conductive layer are over and in contact with a top surface of a same layer.
18. The semiconductor device according to claim 11 ,
wherein the oxide semiconductor layer has depression between the first island-shaped region and the second island-shaped region, and
wherein the insulating layer is in contact with a surface of the depression.
19. The semiconductor device according to claim 11 ,
wherein the conductive layer passes through a first opening in the gate electrode so as to be electrically connected to the second electrode, and
wherein the conductive layer passes through a second opening in the gate electrode so as to be electrically connected to the third electrode.
20. The semiconductor device according to claim 11 , wherein the oxide semiconductor layer comprises a crystal part, a direction of c-axis of the crystal part is substantially parallel to a normal vector of a surface of the oxide semiconductor layer.