It is an object to provide a technique to improve electric characteristics after a high-temperature treatment even when a high melting point metal barrier layer is not formed. A semiconductor device includes a gate electrode formed on a transparent insulation substrate, a semiconductor layer having a Si semiconductor active film and an ohmic low resistance Si film having an n-type conductivity, being formed in this order on the gate electrode with a gate insulation film interposed between the gate electrode and the semiconductor layer, and the source and drain electrodes directly connected to the semiconductor layer and containing at least aluminum (Al). At least nitrogen (N) is contained in a first region that is in the vicinity of an interface between a side surface of the SI semiconductor active film and the source and drain electrodes.