Semiconductor device applying an oxide semiconductor
An object of an embodiment of the present invention is to manufacture a semiconductor device with high display quality and high reliability, which includes a pixel portion and a driver circuit portion capable of high-speed operation over one substrate, using transistors having favorable electric characteristics and high reliability as switching elements. Two kinds of transistors, in each of which an oxide semiconductor layer including a crystalline region on one surface side is used as an active layer, are formed in a driver circuit portion and a pixel portion. Electric characteristics of the transistors can be selected by choosing the position of the gate electrode layer which determines the position of the channel. Thus, a semiconductor device including a driver circuit portion capable of high-speed operation and a pixel portion over one substrate can be manufactured.
1. A semiconductor device comprising:
a first transistor and a second transistor;
the first transistor comprising:
a first conductive layer over a substrate;
a first insulating layer over the first conductive layer;
a first oxide semiconductor layer over the first insulating layer;
a first source electrode layer and a first drain electrode layer each of which has a region overlapping with part of the first oxide semiconductor layer; and
a second insulating layer having a region in contact with part of the first oxide semiconductor layer;
the second transistor comprising:
the first insulating layer over the substrate;
a second oxide semiconductor layer over the first insulating layer;
a second source electrode layer and a second drain electrode layer each of which has a region overlapping with part of the second oxide semiconductor layer; and
the second insulating layer having a region in contact with part of the second oxide semiconductor layer; and
a second conductive layer over the second insulating layer,
wherein a surface portion of the first oxide semiconductor layer comprises a crystal region,
wherein the crystal region comprises a first region in contact with the first source electrode layer, a second region in contact with the first drain electrode layer, and a third region, which is sandwiched between the first region and the second region and overlaps with the first conductive layer, in contact with the second insulating layer, and
wherein the crystal region is c-axis-aligned.
2. The semiconductor device according to claim 1 , wherein the first oxide semiconductor layer comprises indium.
3. The semiconductor device according to claim 2 , wherein the first oxide semiconductor layer further comprises gallium and zinc.
4. The semiconductor device according to claim 1 , wherein the crystal region contains a crystal having a particle size greater than or equal to 1 nm and less than or equal to 20 nm.
5. The semiconductor device according to claim 1 , wherein each of the first conductive layer, the first source electrode layer, the first drain electrode layer, the second source electrode layer, and the second drain electrode layer is a conductive layer having a light transmitting property.
6. The semiconductor device according to claim 1 , wherein the first source electrode layer, the second source electrode layer, the first drain electrode layer, and the second drain electrode layer comprise titanium.
7. The semiconductor device according to claim 1 , wherein the first source electrode layer, the second source electrode layer, the first drain electrode layer, and the second drain electrode layer comprise an element selected from chromium, tantalum, molybdenum, tungsten, and a combination thereof.
8. The semiconductor device according to claim 1 ,
wherein the first oxide semiconductor layer comprises a channel formation region, and
wherein a donor concentration of the channel formation region is lower than or equal to 1×10 18 /cm 3 .
9. A semiconductor device comprising:
a first transistor and a second transistor;
the first transistor comprising:
a first conductive layer over a substrate;
a first insulating layer over the first conductive layer;
a first oxide semiconductor layer over the first insulating layer;
a first source electrode layer and a first drain electrode layer each of which has a region overlapping with part of the first oxide semiconductor layer; and
a second insulating layer having a region in contact with part of the first oxide semiconductor layer;
the second transistor comprising:
the first insulating layer over the substrate;
a second oxide semiconductor layer over the first insulating layer;
a second source electrode layer and a second drain electrode layer each of which has a region overlapping with part of the second oxide semiconductor layer; and
the second insulating layer having a region in contact with part of the second oxide semiconductor layer; and
a second conductive layer over the second insulating layer,
wherein a surface portion of the first oxide semiconductor layer comprises a first crystal region,
wherein the first crystal region comprises a first region in contact with the first source electrode layer, a second region in contact with the first drain electrode layer, and a third region, which is sandwiched between the first region and the second region and overlaps with the first conductive layer, in contact with the second insulating layer,
wherein a surface portion of the second oxide semiconductor layer comprises a second crystal region,
wherein the second crystal region comprises a fourth region in contact with the second source electrode layer, a fifth region in contact with the second drain electrode layer, and a sixth region, which is sandwiched between the fourth region and the fifth region and overlaps with the second conductive layer, in contact with the second insulating layer, and
wherein each of the first crystal region and the second crystal region is c-axis-aligned.
10. The semiconductor device according to claim 9 , wherein the first oxide semiconductor layer comprises indium.
11. The semiconductor device according to claim 10 , wherein the first oxide semiconductor layer further comprises gallium and zinc.
12. The semiconductor device according to claim 9 , wherein each of the first and the second crystal region contains a crystal having a particle size greater than or equal to 1 nm and less than or equal to 20 nm.
13. The semiconductor device according to claim 9 , wherein each of the first conductive layer, the first source electrode layer, the first drain electrode layer, the second source electrode layer, and the second drain electrode layer is a conductive layer having a light transmitting property.
14. The semiconductor device according to claim 9 , wherein the first source electrode layer, the second source electrode layer, the first drain electrode layer, and the second drain electrode layer comprise titanium.
15. The semiconductor device according to claim 9 , wherein the first source electrode layer, the second source electrode layer, the first drain electrode layer, and the second drain electrode layer comprise an element selected from chromium, tantalum, molybdenum, tungsten, and a combination thereof.
16. The semiconductor device according to claim 9 ,
wherein the first oxide semiconductor layer comprises a channel formation region, and
wherein a donor concentration of the channel formation region is lower than or equal to 1×10 18 /cm 3 .
17. A display device comprising:
a first transistor and a second transistor each of which is over a substrate,
the first transistor comprising:
a first conductive layer;
a first oxide semiconductor layer over the first conductive layer;
a first source electrode layer and a first drain electrode layer each of which comprises a region overlapping with the first oxide semiconductor layer; and
a second conductive layer over the first oxide semiconductor layer,
the second transistor comprising:
a second oxide semiconductor layer;
a second source electrode layer and a second drain electrode layer each of which comprises a region overlapping with the second oxide semiconductor layer; and
a third conductive layer over the second oxide semiconductor layer,
wherein the first oxide semiconductor layer comprises a region including a nanocrystal,
wherein the first oxide semiconductor layer comprises a region overlapping with the first conductive layer and the second conductive layer between the first source electrode layer and the first drain electrode layer, and
wherein the second oxide semiconductor layer comprises a region overlapping with the third conductive layer between the second source electrode layer and the second drain electrode layer.
18. The display device according to claim 17 , wherein the nanocrystal has a particle size greater than or equal to 1 nm and less than or equal to 20 nm.
19. The display device according to claim 17 , wherein an end portion of the first oxide semiconductor layer has a tapered shape.
20. The display device according to claim 17 , wherein the first conductive layer contains an element selected from Al, Cr, Ta, Ti, Mo, and W.
21. The display device according to claim 17 , wherein the first source electrode layer and the first drain electrode layer contain an element selected from Al, Cu, Cr, Ta, Ti, Mo, and W.
22. The display device according to claim 17 , wherein the first oxide semiconductor layer has a thickness greater than or equal to 5 nm and less than or equal to 200 nm.
23. The display device according to claim 17 ,
wherein the first oxide semiconductor layer comprises a first region including a first crystal and a second region including a second crystal, and
wherein a crystal state of the first region is different from the crystal state of the second region.
24. The display device according to claim 17 ,
wherein the first oxide semiconductor layer comprises a region overlapping with the first conductive layer with a first insulating layer provided therebetween, and
wherein the first insulating layer comprises silicon oxide.
25. The display device according to claim 17 ,
wherein the first oxide semiconductor layer comprises a region overlapping with the second conductive layer with a second insulating layer provided therebetween, and
wherein the second insulating layer comprises silicon oxide.
26. A display device comprising:
a first transistor and a second transistor each of which is over a substrate,
the first transistor comprising:
a first conductive layer;
a first oxide semiconductor layer over the first conductive layer;
a first source electrode layer and a first drain electrode layer each of which comprises a region overlapping with the first oxide semiconductor layer; and
a second conductive layer over the first oxide semiconductor layer,
the second transistor comprising:
a second oxide semiconductor layer;
a second source electrode layer and a second drain electrode layer each of which comprises a region overlapping with the second oxide semiconductor layer; and
a third conductive layer over the second oxide semiconductor layer,
wherein the first oxide semiconductor layer comprises a region including a crystal with a particle size greater than or equal to 1 nm and less than or equal to 20 nm,
wherein the first oxide semiconductor layer comprises a region overlapping with the first conductive layer and the second conductive layer between the first source electrode layer and the first drain electrode layer, and
wherein the second oxide semiconductor layer comprises a region overlapping with the third conductive layer between the second source electrode layer and the second drain electrode layer.
27. The display device according to claim 26 , wherein an end portion of the first oxide semiconductor layer has a tapered shape.
28. The display device according to claim 26 , wherein the first conductive layer contains an element selected from Al, Cr, Ta, Ti, Mo, and W.
29. The display device according to claim 26 , wherein the first source electrode layer and the first drain electrode layer contain an element selected from Al, Cu, Cr, Ta, Ti, Mo, and W.
30. The display device according to claim 26 , wherein the first oxide semiconductor layer has a thickness greater than or equal to 5 nm and less than or equal to 200 nm.
31. The display device according to claim 26 ,
wherein the first oxide semiconductor layer comprises a first region including a first crystal and a second region including a second crystal, and
wherein a crystal state of the first region is different from the crystal state of the second region.
32. The display device according to claim 26 ,
wherein the first oxide semiconductor layer comprises a region overlapping with the first conductive layer with a first insulating layer provided therebetween, and
wherein the first insulating layer comprises silicon oxide.
33. The display device according to claim 26 ,
wherein the first oxide semiconductor layer comprises a region overlapping with the second conductive layer with a second insulating layer provided therebetween, and
wherein the second insulating layer comprises silicon oxide.