Patent ID: 8748223

Claim:
A method for manufacturing a semiconductor device, comprising the steps of: forming a gate electrode over a substrate; forming a gate insulating film over the gate electrode; forming an oxide semiconductor film over the gate insulating film by a sputtering method using an oxide semiconductor target in a chamber; forming a source electrode and a drain electrode over the oxide semiconductor film; forming a silicon oxide film over the source electrode and the drain electrode while the substrate is heated at 200° C. to 400° C.; and forming a silicon nitride film over the silicon oxide film while the substrate is heated at 200° C. to 400° C., wherein a filling rate of the oxide semiconductor target is greater than or equal to 90%, wherein the chamber is evacuated with use of a cryopump, and wherein, when the oxide semiconductor film is formed, a sputtering gas from which hydrogen and moisture are removed is introduced into the chamber.