Method for manufacturing semiconductor device

1. A method for manufacturing a semiconductor device, comprising the steps of:

forming a gate electrode;

forming a first insulating film over the gate electrode;

performing halogen doping treatment on the first insulating film so that the first insulating film is supplied with a halogen atom;

forming an oxide semiconductor film over the first insulating film so that the oxide semiconductor film overlaps with the gate electrode;

performing first heat treatment on the oxide semiconductor film so that a hydrogen atom in the oxide semiconductor film is removed;

performing oxygen doping treatment on the oxide semiconductor film from which the hydrogen atom is removed so that the oxide semiconductor film is supplied with an oxygen atom;

performing second heat treatment on the oxide semiconductor film to which the oxygen atom is supplied;

forming a source electrode and a drain electrode on and in contact with the oxide semiconductor film; and

forming a second insulating film on and in contact with the oxide semiconductor film.

2. The method for manufacturing a semiconductor device, according to claim 1 , further comprising the step of forming a third insulating film containing nitrogen so that the third insulating film containing nitrogen covers the second insulating film.

3. The method for manufacturing a semiconductor device, according to claim 1 , further comprising the step of processing the oxide semiconductor film into an island-shaped oxide semiconductor film.

4. The method for manufacturing a semiconductor device, according to claim 3 , wherein at least part of the first insulating film is processed into an island-shaped first insulating film in the step of processing the oxide semiconductor film into the island-shaped oxide semiconductor film.

5. The method for manufacturing a semiconductor device, according to claim 3 , wherein the second insulating film is in contact with the first insulating film.

6. The method for manufacturing a semiconductor device, according to claim 1 , wherein at least one of the first insulating film and the second insulating film contains a constituent element of the oxide semiconductor film.

7. The method for manufacturing a semiconductor device, according to claim 1 , wherein at least one of the first insulating film and the second insulating film has a stacked-layer structure comprising a third insulating film containing a constituent element of the oxide semiconductor film and a fourth insulating film containing an element different from the constituent element of the oxide semiconductor film.

8. The method for manufacturing a semiconductor device, according to claim 1 , wherein at least one of the first insulating film and the second insulating film contains gallium.

9. The method for manufacturing a semiconductor device, according to claim 1 , wherein at least one of the first insulating film and the second insulating film has a stacked-layer structure comprising a third insulating film containing gallium and a fourth insulating film containing a material different from gallium.

10. The method for manufacturing a semiconductor device, according to claim 1 , wherein chlorine is used in the halogen doping treatment.

11. The method for manufacturing a semiconductor device, according to claim 1 , further comprising the step of forming a third insulating film over the first insulating film.

12. The method for manufacturing a semiconductor device, according to claim 11 ,

wherein the first insulating film contains an element different from a constituent element of the oxide semiconductor film, and

wherein the third insulating film contains the constituent element of the oxide semiconductor film.

13. The method for manufacturing a semiconductor device, according to claim 11 ,

wherein the first insulating film contains a material different from gallium, and

wherein the third insulating film contains gallium.