Semiconductor device
Defects in an oxide semiconductor film are reduced in a semiconductor device including the oxide semiconductor film. The electrical characteristics of a semiconductor device including an oxide semiconductor film are improved. The reliability of a semiconductor device including an oxide semiconductor film is improved. A semiconductor device including an oxide semiconductor layer; a metal oxide layer in contact with the oxide semiconductor layer, the metal oxide layer including an In-M oxide (M is Ti, Ga, Y, Zr, La, Ce, Nd, or Hf); and a conductive layer in contact with the metal oxide layer, the conductive layer including copper, aluminum, gold, or silver is provided. In the semiconductor device, y/(x+y) is greater than or equal to 0.75 and less than 1 where the atomic ratio of In to M included in the metal oxide layer is In:M=x:y.
1. A semiconductor device comprising:
a transistor that comprises:
a gate electrode;
a gate insulating layer over the gate electrode;
an oxide semiconductor layer over and in contact with the gate insulating layer, the oxide semiconductor layer comprising In, Ga and Zn;
an oxide layer over the oxide semiconductor layer, the oxide layer comprising In and Ga;
a first conductive layer in contact with a top surface of the oxide layer, a side surface of the oxide layer, and a side surface of the oxide semiconductor layer; and
a second conductive layer in contact with a top surface of the oxide layer, a side surface of the oxide layer, and a side surface of the oxide semiconductor layer,
wherein y1/x1 is greater than or equal to 1 and less than 3 where an atomic ratio of In to Ga included in the oxide semiconductor layer is In:Ga=x1:y1, and
wherein y2/(x2+y2) is greater than or equal to 0.80 and less than 0.90 where an atomic ratio of In to Ga included in the oxide layer is In:Ga=x2:y2.
2. The oxide layer according to claim 1 , wherein the oxide layer does not comprise Zn.
3. The semiconductor device according to claim 1 , wherein each of the first conductive layer and the second conductive layer comprises a stack of a titanium layer and a copper layer over the titanium layer.
4. The semiconductor device according to claim 1 , wherein a conductivity of the oxide layer is lower than a conductivity of the oxide semiconductor layer.
5. The semiconductor device according to claim 1 , wherein off-state current of the transistor is less than or equal to 1×10 −13 A at a voltage between a source of the transistor and a drain of the transistor is 10 V.
6. A semiconductor device comprising:
an oxide semiconductor layer comprising a channel formation region;
an oxide layer over the oxide semiconductor layer, the oxide layer comprising In and Ga; and
a gate electrode overlapping with the oxide semiconductor layer and the oxide layer,
wherein y/(x+y) is greater than or equal to 0.80 and less than 0.90 where an atomic ratio of In to Ga included in the oxide layer is In:Ga=x:y.
7. The semiconductor device according to claim 6 , wherein the oxide layer does not comprise Zn.
8. The semiconductor device according to claim 6 , wherein the oxide semiconductor layer comprises In, Ga and Zn.
9. The semiconductor device according to claim 6 , wherein a conductivity of the oxide layer is lower than a conductivity of the oxide semiconductor layer.
10. A semiconductor device comprising:
an oxide semiconductor layer comprising a channel formation region;
an oxide layer over the oxide semiconductor layer, the oxide layer comprising In and Ga; and
an electrode over the oxide layer and electrically connected to the oxide semiconductor layer,
wherein y/(x+y) is greater than or equal to 0.80 and less than 0.90 where an atomic ratio of In to Ga included in the oxide layer is In:Ga=x:y,
wherein the oxide layer is located between the oxide semiconductor layer and the electrode, and
wherein the electrode comprise Cu.
11. The semiconductor device according to claim 10 , wherein the oxide layer does not comprise Zn.
12. The semiconductor device according to claim 10 , wherein the oxide semiconductor layer comprises In, Ga and Zn.
13. The semiconductor device according to claim 10 , wherein a conductivity of the oxide layer is lower than a conductivity of the oxide semiconductor layer.
14. A semiconductor device comprising:
a transistor that comprises:
a gate electrode;
a gate insulating layer over the gate electrode;
an oxide semiconductor layer over and in contact with the gate insulating layer, the oxide semiconductor layer comprising In, Ga and Zn;
an oxide layer over the oxide semiconductor layer, the oxide layer comprising In and Ga;
a first conductive layer in contact with a top surface of the oxide layer, a side surface of the oxide layer, and a side surface of the oxide semiconductor layer; and
a second conductive layer in contact with a top surface of the oxide layer, a side surface of the oxide layer, and a side surface of the oxide semiconductor layer,
wherein y1/x1 is greater than or equal to 1 and less than 3 where an atomic ratio of In to Ga included in the oxide semiconductor layer is In:Ga=x1:y1,
wherein y2/(x2+y2) is greater than or equal to 0.80 and less than 0.90 where an atomic ratio of In to Ga included in the oxide layer is In:Ga=x2:y2, and
wherein a thickness of the oxide layer is greater than or equal to 10 nm and less than or equal to 100 nm.
15. The semiconductor device according to claim 14 , wherein the oxide layer does not comprise Zn.
16. The semiconductor device according to claim 14 , wherein each of the first conductive layer and the second conductive layer comprises a stack of a titanium layer and a copper layer over the titanium layer.
17. The semiconductor device according to claim 14 , wherein a conductivity of the oxide layer is lower than a conductivity of the oxide semiconductor layer.
18. The semiconductor device according to claim 14 , wherein off-state current of the transistor is less than or equal to 1×10 −13 A at a voltage between a source of the transistor and a drain of the transistor is 10 V.