An object is to provide a field effect transistor (FET) having a conductor-semiconductor junction, which has excellent characteristics, which can be manufactured through an easy process, or which enables high integration. Owing to the junction between a semiconductor layer and a conductor having a work function lower than the electron affinity of the semiconductor layer, a region into which carriers are injected from the conductor is formed in the semiconductor layer. Such a region is used as an offset region of the FET or a resistor of a semiconductor circuit such as an inverter. Further, in the case of setting up such an offset region and a resistor in one semiconductor layer, an integrated semiconductor device can be manufactured.