Semiconductor device and display device including the semiconductor device
The reliability of a transistor including an oxide semiconductor is improved. The transistor in a semiconductor device includes a first oxide semiconductor film over a first insulating film, a gate insulating film over the first oxide semiconductor film, a second oxide semiconductor film over the gate insulating film, and a second insulating film over the first oxide semiconductor film and the second oxide semiconductor film. The first oxide semiconductor film includes a channel region overlapping with the second oxide semiconductor film, a source region and a drain region each in contact with the second insulating film. The channel region includes a first layer and a second layer in contact with a top surface of the first layer and covering a side surface of the first layer in the channel width direction. The second oxide semiconductor film has a higher carrier density than the first oxide semiconductor film.
1. A semiconductor device comprising a transistor,
wherein the transistor comprises:
a first oxide semiconductor film over a first insulating film;
a gate insulating film over the first oxide semiconductor film;
a second oxide semiconductor film over the gate insulating film; and
a second insulating film over the first oxide semiconductor film and the second oxide semiconductor film,
wherein the first oxide semiconductor film comprises:
a channel region overlapping with the second oxide semiconductor film;
a source region in contact with the second insulating film; and
a drain region in contact with the second insulating film,
wherein the channel region comprises:
a first layer; and
a second layer which is in contact with a top surface of the first layer and covers a side surface of the first layer in a channel width direction, and
wherein the second oxide semiconductor film has a higher carrier density than the first oxide semiconductor film, and
wherein the second oxide semiconductor film comprises a plurality of crystals.
2. The semiconductor device according to claim 1 , further comprising a region in which an upper end portion of the gate insulating film is aligned with or positioned further outward than a lower end portion of the second oxide semiconductor film.
3. The semiconductor device according to claim 1 , wherein the second insulating film comprises at least one of nitrogen and hydrogen.
4. The semiconductor device according to claim 1 , wherein the transistor further comprises:
a third insulating film over the second insulating film;
a source electrode connected to the source region through an opening in the second insulating film and the third insulating film; and
a drain electrode connected to the drain region through an opening in the second insulating film and the third insulating film.
5. The semiconductor device according to claim 1 , wherein the source region and the drain region each comprise a region having the same hydrogen concentration as the second oxide semiconductor film.
6. The semiconductor device according to claim 1 , wherein the source region and the drain region each comprise at least one of hydrogen, boron, carbon, nitrogen, fluorine, phosphorus, sulfur, and a rare gas.
7. The semiconductor device according to claim 1 , wherein at least one of the first oxide semiconductor film and the second oxide semiconductor film comprises oxygen, In, Zn, and M (M is Al, Ga, Y, or Sn).
8. The semiconductor device according to claim 1 ,
wherein each of c-axes of the plurality of the crystals in the second oxide semiconductor film is substantially perpendicular to an upper surface of the second oxide semiconductor film.
9. A semiconductor device comprising a transistor,
wherein the transistor comprises:
a first oxide semiconductor film over a first insulating film;
a gate insulating film over the first oxide semiconductor film;
a second oxide semiconductor film over the gate insulating film; and
a second insulating film over the first oxide semiconductor film and the second oxide semiconductor film,
wherein the first oxide semiconductor film comprises:
a channel region overlapping with the second oxide semiconductor film;
a source region in contact with the second insulating film; and
a drain region in contact with the second insulating film,
wherein the channel region comprises:
a first layer;
a second layer which is in contact with a top surface of the first layer and covers a side surface of the first layer in a channel width direction; and
a third layer in contact with a bottom surface of the first layer, and
wherein the second oxide semiconductor film has a higher carrier density than the first oxide semiconductor film, and
wherein the second oxide semiconductor film comprises a plurality of crystals.
10. The semiconductor device according to claim 9 , further comprising a region in which an upper end portion of the gate insulating film is aligned with or positioned further outward than a lower end portion of the second oxide semiconductor film.
11. The semiconductor device according to claim 9 , wherein the second insulating film comprises at least one of nitrogen and hydrogen.
12. The semiconductor device according to claim 9 , wherein the transistor further comprises:
a third insulating film over the second insulating film;
a source electrode connected to the source region through an opening in the second insulating film and the third insulating film; and
a drain electrode connected to the drain region through an opening in the second insulating film and the third insulating film.
13. The semiconductor device according to claim 9 , wherein the source region and the drain region each comprise a region having the same hydrogen concentration as the second oxide semiconductor film.
14. The semiconductor device according to claim 9 , wherein the source region and the drain region each comprise at least one of hydrogen, boron, carbon, nitrogen, fluorine, phosphorus, sulfur, and a rare gas.
15. The semiconductor device according to claim 9 , wherein at least one of the first oxide semiconductor film and the second oxide semiconductor film comprises oxygen, In, Zn, and M (M is Al, Ga, Y, or Sn).
16. The semiconductor device according to claim 9 ,
wherein each of c-axes of the plurality of the crystals in the second oxide semiconductor film is substantially perpendicular to an upper surface of the second oxide semiconductor film.