Field effect transistor and method for manufacturing the same
View Patent ↗Provided is a novel structure of a field effect transistor using a metal-semiconductor junction. The field effect transistor includes a wiring which is provided over a substrate and also functions as a gate electrode; an insulating film which is provided over the wiring, has substantially the same shape as the wiring, and also functions as a gate insulating film; a semiconductor layer which is provided over the insulating film and includes an oxide semiconductor and the like; an oxide insulating layer which is provided over the semiconductor layer and whose thickness is 5 times or more as large as the sum of the thickness of the insulating film and the thickness of the semiconductor layer or 100 nm or more; and wirings which are connected to the semiconductor layer through openings provided in the oxide insulating layer.
1. A method for manufacturing a field effect transistor comprising the steps of:
forming a first conductive layer over a substrate;
forming an insulating film over the first conductive layer;
patterning the insulating film and then patterning the first conductive layer so that the patterned first conductive layer has substantially the same shape as the patterned insulating film;
forming a semiconductor layer over and in contact with the patterned insulating film so that the semiconductor layer does not overlap with any side edge of the patterned first conductive layer;
forming an oxide insulating layer over the semiconductor layer;
providing an opening reaching the semiconductor layer in the oxide insulating layer; and
forming a second conductive layer covering the oxide insulating layer.
2. The method for manufacturing a field effect transistor, according to claim 1 , further comprising a step of:
heating the oxide insulating layer at a temperature which is 200° C. or higher.
3. The method for manufacturing a field effect transistor, according to claim 1 , wherein the oxide insulating layer is formed by a sputtering method.
4. The method for manufacturing a field effect transistor, according to claim 1 , wherein the semiconductor layer is formed so that the semiconductor layer does not cross any side edge of the insulating film.
5. The method for manufacturing a field effect transistor, according to claim 1 , wherein the opening is directly in contact with a surface of the semiconductor layer.
6. The method for manufacturing a field effect transistor, according to claim 1 , further comprising a step of:
diffusing oxygen by heating the oxide insulating layer.
7. The method for manufacturing a field effect transistor, according to claim 1 , wherein the first conductive layer and the insulating film are successively formed without exposing the substrate to the air.
8. The method for manufacturing a field effect transistor, according to claim 1 , wherein the opening does not overlap with any side edge of the semiconductor layer.
9. A method for manufacturing a field effect transistor comprising the steps of:
forming a first conductive layer over a substrate;
forming an insulating film over the first conductive layer;
forming an insulating layer by patterning the insulating film and then forming a wiring by patterning the first conductive layer by using the insulating layer as a mask;
forming a semiconductor layer over and in contact with the insulating layer so that the semiconductor layer does not overlap with any side edge of the wiring;
forming an oxide insulating layer over the semiconductor layer;
providing an opening reaching the semiconductor layer in the oxide insulating layer; and
forming a second conductive layer covering the oxide insulating layer.
10. The method for manufacturing a field effect transistor, according to claim 9 , further comprising a step of:
heating the oxide insulating layer at a temperature of 200° C. or higher.
11. The method for manufacturing a field effect transistor, according to claim 9 , wherein the oxide insulating layer is formed by a sputtering method.
12. The method for manufacturing a field effect transistor, according to claim 9 , wherein the semiconductor layer is formed so that the semiconductor layer does not cross any side edge of the insulating layer.
13. The method for manufacturing a field effect transistor, according to claim 9 , wherein the opening is directly in contact with a surface of the semiconductor layer.
14. The method for manufacturing a field effect transistor, according to claim 9 , further comprising a step of:
diffusing oxygen by heating the oxide insulating layer.
15. The method for manufacturing a field effect transistor, according to claim 9 , wherein the first conductive layer and the insulating film are successively formed without exposing the substrate to the air.
16. The method for manufacturing a field effect transistor, according to claim 9 , wherein the opening does not overlap with any side edge of the semiconductor layer.
17. A method for manufacturing a field effect transistor comprising the steps of:
forming a first conductive layer over a substrate;
forming an insulating film over the first conductive layer;
forming an insulating layer by patterning the insulating film and then forming a wiring by patterning the first conductive layer with a resist mask over the insulating layer;
forming a semiconductor layer over and in contact with the insulating layer so that the semiconductor layer does not overlap with any side edge of the wiring;
forming an oxide insulating layer over the semiconductor layer;
providing an opening reaching the semiconductor layer in the oxide insulating layer; and
forming a second conductive layer covering the oxide insulating layer.
18. The method for manufacturing a field effect transistor, according to claim 17 , further comprising a step of:
heating the oxide insulating layer at a temperature of 200° C. or higher.
19. The method for manufacturing a field effect transistor, according to claim 17 , wherein the oxide insulating layer is formed by a sputtering method.
20. The method for manufacturing a field effect transistor, according to claim 17 , wherein the semiconductor layer is formed so that the semiconductor layer does not cross any side edge of the insulating layer.
21. The method for manufacturing a field effect transistor, according to claim 17 , wherein the opening is directly in contact with a surface of the semiconductor layer.
22. The method for manufacturing a field effect transistor, according to claim 17 , further comprising a step of:
diffusing oxygen by heating the oxide insulating layer.
23. The method for manufacturing a field effect transistor, according to claim 17 , wherein the first conductive layer and the insulating film are successively formed without exposing the substrate to the air.
24. The method for manufacturing a field effect transistor, according to claim 17 , wherein the opening does not overlap with any side edge of the semiconductor layer.