A semiconductor device include a substrate, a buffer layer formed on the substrate, a channel layer formed by an intrinsic polycrystalline silicon layer on the buffer layer, polycrystalline source and drain by non-intrinsic silicon formed on both sides of the polycrystalline silicon layer, a source electrode and a drain electrode formed on the polycrystalline source and the drain, a gate electrode corresponding to the channel layer, and an NiSi2 contact layer located between the source and the source electrode and between the drain and the drain electrode.