| abstract |
A semiconductor device in which variation in threshold voltage of a transistor is suppressed is provided. In addition, a semiconductor device in which a decrease in on-state current of a transistor is suppressed is provided. A gate electrode layer is formed over a substrate, a gate insulating film is formed over the gate electrode layer, an oxide semiconductor film is formed over the gate insulating film, and an oxide semiconductor is formed over the oxide semiconductor film. A metal oxide film is formed by reducing the metal oxide film by performing a heat treatment in a state where the metal oxide film and the oxide semiconductor film are in contact with each other. The source electrode layer and the drain electrode layer are formed by processing the metal film. [Selection] Figure 1 |