US Patent 8492756 Semiconductor device and method for manufacturing the same

An object is to provide a semiconductor device including a thin film transistor which includes an oxide semiconductor layer and has high electric characteristics. An oxide semiconductor layer including SiOx is used in a channel formation region, and in order to reduce contact resistance with source and drain electrode layers formed using a metal material with low electric resistance, source and drain regions are provided between the source and drain electrode layers and the oxide semiconductor layer including SiOx. The source and drain regions are formed using an oxide semiconductor layer which does not include SiOx or an oxynitride film.