| abstract |
A semiconductor device with high reliability, low leakage current between a source and a drain, and low contact resistance is provided. A first insulating film and a second insulating film provided in contact with an oxide semiconductor film are stacked over an electrode film of a transistor formed using an oxide semiconductor film, and a second insulating film is formed. An etching mask is formed over the insulating film, and an opening that exposes the electrode film is formed by etching the first insulating film and the second insulating film in a portion overlapping with the opening of the etching mask. The openings of the film and the second insulating film are exposed to argon plasma, the etching mask is removed, a conductive film is formed in the openings of the first insulating film and the second insulating film, and the first insulating film is heated. Therefore, the second insulating film is less likely to be etched than the first insulating film and has lower gas permeability than the first insulating film. Alternatively, reverse sputtering may be performed. [Selection] Figure 4 |