A semiconductor device and fabrication method thereof. The semiconductor device comprises a substrate, an electroactive organic layer with conformal step coverage and uniform thickness, and a metal layer. The substrate is a conductive substrate or a nonconductive substrate with a conductive layer formed thereon. The electroactive organic layer and the metal layer are formed sequentially on the conductive substrate or the conductive layer, wherein the electroactive organic layer comprises metal atoms and serves as a seed layer, resulting in the metal layer formed in-situ.