Semiconductor device and method for manufacturing the same

A highly reliable semiconductor device and a method for manufacturing the semiconductor device are provided. The semiconductor device is manufactured with a high yield to achieve high productivity. In the manufacture of a semiconductor device including a transistor in which a gate electrode layer, a gate insulating film, and an oxide semiconductor film are sequentially stacked and a source electrode layer and a drain electrode layer are provided in contact with the oxide semiconductor film, the source electrode layer and the drain electrode layer are formed through an etching step and then a step for removing impurities which are generated by the etching step and exist on a surface of the oxide semiconductor film and in the vicinity thereof is performed.