Semiconductor device and manufacturing method thereof
In a semiconductor device, a region where a channel is formed is protected. In a semiconductor device, a region protecting a region where a channel is formed is provided in a semiconductor layer. In a semiconductor device, a layer protecting a region where a channel is formed is provided. In a semiconductor device, a region and/or a layer protecting a region where a channel is formed have/has a low density of defect states. In a semiconductor device, a region where a channel is formed has a low density of defect states.
1. A method for manufacturing a semiconductor device comprising the steps of:
forming a gate electrode;
forming a gate insulating film over the gate electrode;
forming a first oxide semiconductor layer over the gate insulating film and forming a second oxide semiconductor layer over the first oxide semiconductor layer so that a mixed region where energy is continuously changed in a band structure is formed between the first oxide semiconductor layer and the second oxide semiconductor layer,
forming a conductive film over the second oxide semiconductor layer; and
partly etching the conductive film to expose a part of the second oxide semiconductor layer,
wherein the part of the second oxide semiconductor layer is etched so that a thickness of the part of the second oxide semiconductor layer is greater than 0 nm and less than 5 nm.
2. The method for manufacturing a semiconductor device according to claim 1 ,
wherein the second oxide semiconductor layer comprises a region having a larger energy gap than the energy gap of the first oxide semiconductor layer.
3. The method for manufacturing a semiconductor device according to claim 1 ,
wherein the second oxide semiconductor layer and the first oxide semiconductor layer comprise indium and an element M selected from aluminum, gallium, yttrium, zirconium, and tin, and
wherein the second oxide semiconductor layer comprises a region where a proportion of the element M is higher than a proportion of the element M in the first oxide semiconductor layer.
4. The method for manufacturing a semiconductor device according to claim 1 ,
wherein the second oxide semiconductor layer is formed by a sputtering method at a substrate temperature of higher than or equal to 100° C. and lower than 500° C.
5. The method for manufacturing a semiconductor device according to claim 1 ,
wherein the part of the second oxide semiconductor layer is etched with use of a solution containing at least one of phosphoric acid, nitric acid, hydrofluoric acid, hydrochloric acid, sulfuric acid, acetic acid, and oxalic acid.
6. The method for manufacturing a semiconductor device according to claim 1 , further comprising the step of:
performing a heat treatment after forming the second oxide semiconductor layer and before forming the conductive film.
7. The method for manufacturing a semiconductor device according to claim 1 , wherein both of the first oxide semiconductor layer and the second oxide semiconductor layer include a c-axis aligned crystalline oxide semiconductor.
8. A method for manufacturing a semiconductor device comprising the steps of:
forming a conductive layer;
forming an insulating film over the conductive layer;
forming a first oxide semiconductor layer over the insulating film;
forming a second oxide semiconductor layer over the first oxide semiconductor layer so that a mixed region where energy is continuously changed in a band structure is formed between the first oxide semiconductor layer and the second oxide semiconductor layer;
forming a conductive film over the second oxide semiconductor layer; and
partly etching the conductive film to expose a part of the second oxide semiconductor layer,
wherein the part of the second oxide semiconductor layer is etched so that a thickness of the part of the second oxide semiconductor layer is greater than 0 nm and less than 5 nm.
9. The method for manufacturing a semiconductor device according to claim 8 ,
wherein the second oxide semiconductor layer comprises a region having a larger energy gap than the energy gap of the first oxide semiconductor layer.
10. The method for manufacturing a semiconductor device according to claim 8 ,
wherein the second oxide semiconductor layer and the first oxide semiconductor layer comprise indium and an element M selected from aluminum, gallium, yttrium, zirconium, and tin, and
wherein the second oxide semiconductor layer comprises a region where a proportion of the element M is higher than a proportion of the element M in the first oxide semiconductor layer.
11. The method for manufacturing a semiconductor device according to claim 8 ,
wherein the second oxide semiconductor layer is formed by a sputtering method at a substrate temperature of higher than or equal to 100° C. and lower than 500° C.
12. The method for manufacturing a semiconductor device according to claim 8 ,
wherein the part of the second oxide semiconductor layer is etched with use of a solution containing at least one of phosphoric acid, nitric acid, hydrofluoric acid, hydrochloric acid, sulfuric acid, acetic acid, and oxalic acid.
13. The method for manufacturing a semiconductor device according to claim 8 , further comprising the step of:
performing a heat treatment after forming the second oxide semiconductor layer and before forming the conductive film.
14. The method for manufacturing a semiconductor device according to claim 8 , wherein both of the first oxide semiconductor layer and the second oxide semiconductor layer include a c-axis aligned crystalline oxide semiconductor.
15. A method for manufacturing a semiconductor device comprising the steps of:
forming a conductive layer;
forming an insulating film over the conductive layer;
forming a first oxide semiconductor layer over the insulating film;
forming a second oxide semiconductor layer over the first oxide semiconductor layer so that a mixed region where energy is continuously changed in a band structure is formed between the first oxide semiconductor layer and the second oxide semiconductor layer;
forming a conductive film over the second oxide semiconductor layer;
partly etching the conductive film to expose a part of the second oxide semiconductor layer; and
etching the part of the second oxide semiconductor layer so that a thickness of the part of the second oxide semiconductor layer is greater than 0 nm and less than 5 nm.
16. The method for manufacturing a semiconductor device according to claim 15 ,
wherein the second oxide semiconductor layer comprises a region having a larger energy gap than the energy gap of the first oxide semiconductor layer.
17. The method for manufacturing a semiconductor device according to claim 15 ,
wherein the second oxide semiconductor layer and the first oxide semiconductor layer comprise indium and an element M selected from aluminum, gallium, yttrium, zirconium, and tin, and
wherein the second oxide semiconductor layer comprises a region where a proportion of the element M is higher than a proportion of the element M in the first oxide semiconductor layer.
18. The method for manufacturing a semiconductor device according to claim 15 ,
wherein the second oxide semiconductor layer is formed by a sputtering method at a substrate temperature of higher than or equal to 100° C. and lower than 500° C.
19. The method for manufacturing a semiconductor device according to claim 15 ,
wherein the part of the second oxide semiconductor layer is etched with use of a solution containing at least one of phosphoric acid, nitric acid, hydrofluoric acid, hydrochloric acid, sulfuric acid, acetic acid, and oxalic acid.
20. The method for manufacturing a semiconductor device according to claim 15 , further comprising the step of:
performing a heat treatment after forming the second oxide semiconductor layer and before forming the conductive film.
21. The method for manufacturing a semiconductor device according to claim 15 , wherein both of the first oxide semiconductor layer and the second oxide semiconductor layer include a c-axis aligned crystalline oxide semiconductor.