Patent ID: 8293595

Claim:
A method for manufacturing a semiconductor device, comprising the steps of: forming a gate electrode over a substrate having an insulating surface; forming a stacked layer in which a first insulating film is formed over the gate electrode, an oxide semiconductor layer is formed over the first insulating film, and a second insulating film is formed over the oxide semiconductor layer by sputtering without being exposed to air; forming a protective film in a region overlapping with the gate electrode by selectively etching the second insulating film; etching an upper layer of the oxide semiconductor layer with the protective film as a mask; forming a conductive film over the oxide semiconductor layer and the protective film; and selectively etching the conductive film with the protective film used as an etching stopper, wherein at least one of the first insulating film and the second insulating film is formed under an atmosphere including only oxygen or an atmosphere including oxygen at 90% or more and an inert gas at 10% or less by the sputtering method.