Semiconductor device

1. A semiconductor device comprising:

a first insulator;

a first oxide over the first insulator;

a second oxide over the first oxide;

a third oxide and a fourth oxide over the second oxide;

a first conductor over the third oxide, the first conductor functioning as one of a source electrode and a drain electrode;

a second conductor over the fourth oxide, the second conductor functioning as the other of the source electrode and the drain electrode;

a fifth oxide over the second oxide;

a second insulator over the fifth oxide, the second insulator functioning as a gate insulator; and

a third conductor over the second insulator, the third conductor functioning as a gate electrode,

wherein the fifth oxide is in contact with a side surface of the third oxide and a side surface of the fourth oxide,

wherein a conductivity of the third oxide is higher than a conductivity of the second oxide,

wherein a conductivity of the fourth oxide is higher than a conductivity of the second oxide,

wherein the second oxide comprises In, an element M, and Zn,

wherein the element M is Al, Ga, Y, or Sn, and

wherein each of the third oxide and the fourth oxide comprises Zn.

2. The semiconductor device according to claim 1 ,

wherein the third oxide comprises a first region not overlapping with the first conductor,

wherein the fourth oxide comprises a second region not overlapping with the second conductor, and

wherein the fifth oxide is in contact with each of a top surface of the first region and a top surface of the second region.

3. The semiconductor device according to claim 1 ,

wherein the third oxide comprises a first region not overlapping with the first conductor,

wherein the fourth oxide comprises a second region not overlapping with the second conductor, and

wherein the fifth oxide is in contact with a top surface of the first region and a top surface of the second region.

4. The semiconductor device according to claim 1 ,

wherein a thickness of each of the third oxide and the fourth oxide is greater than or equal to 1 nm and less than or equal to 10 nm.

5. The semiconductor device according to claim 1 ,

wherein each of the third oxide and the fourth oxide has crystallinity.

6. The semiconductor device according to claim 1 , wherein the fifth oxide, the second insulator, and the third conductor are positioned between the third oxide and the fourth oxide.

7. A semiconductor device comprising:

a first insulator;

a first oxide over the first insulator;

a second oxide over the first oxide;

a third oxide and a fourth oxide over the second oxide;

a first conductor over the third oxide, the first conductor functioning as one of a source electrode and a drain electrode;

a second conductor over the fourth oxide, the second conductor functioning as the other of the source electrode and the drain electrode;

a fifth oxide over the second oxide;

a second insulator over the fifth oxide, the second insulator functioning as a gate insulator; and

a third conductor over the second insulator, the third conductor functioning as a gate electrode,

wherein the fifth oxide is in contact with a side surface of the third oxide and a side surface of the fourth oxide,

wherein a conductivity of the third oxide is higher than a conductivity of the second oxide, and

wherein a conductivity of the fourth oxide is higher than a conductivity of the second oxide.

8. The semiconductor device according to claim 7 , wherein a thickness of each of the third oxide and the fourth oxide is greater than or equal to 1 nm and less than or equal to 10 nm.

9. The semiconductor device according to claim 7 , wherein each of the third oxide and the fourth oxide has crystallinity.

10. The semiconductor device according to claim 7 , wherein the fifth oxide, the second insulator, and the third conductor are positioned between the third oxide and the fourth oxide.

11. A semiconductor device comprising:

a first insulator;

a first oxide over the first insulator;

a second oxide over the first oxide;

a third oxide and a fourth oxide over the second oxide;

a first conductor over the third oxide, the first conductor functioning as one of a source electrode and a drain electrode;

a second conductor over the fourth oxide, the second conductor functioning as the other of the source electrode and the drain electrode;

a fifth oxide over the second oxide;

a second insulator over the fifth oxide, the second insulator functioning as a gate insulator; and

a third conductor over the second insulator, the third conductor functioning as a gate electrode,

wherein the fifth oxide is in contact with a side surface of the third oxide and a side surface of the fourth oxide,

wherein the second oxide comprises In, an element M, and Zn,

wherein the element M is Al, Ga, Y, or Sn, and

wherein each of the third oxide and the fourth oxide comprises Zn.

12. The semiconductor device according to claim 11 ,

wherein the third oxide comprises a first region not overlapping with the first conductor,

wherein the fourth oxide comprises a second region not overlapping with the second conductor, and

wherein the fifth oxide is in contact with a top surface of the first region and a top surface of the second region.

13. The semiconductor device according to claim 11 , wherein a thickness of each of the third oxide and the fourth oxide is greater than or equal to 1 nm and less than or equal to 10 nm.

14. The semiconductor device according to claim 11 , wherein each of the third oxide and the fourth oxide has crystallinity.

15. The semiconductor device according to claim 11 , wherein the fifth oxide, the second insulator, and the third conductor are positioned between the third oxide and the fourth oxide.