In a power MOS transistor, for example, a source electrode is formed so as to be commonly connected to a plurality of source regions formed on the front surface. Thus, a current density varies based on in-plane resistance of the source electrode, thereby providing the necessity of increasing the number of wires connecting the sources and a lead. In the invention, an electrode structure includes a copper plating layer 10e formed on a pad electrode 10a by an electrolytic plating method, and a nickel plating layer 10f and a gold plating layer formed so as to cover the upper and side surfaces of the copper plating layer 10e by an electroless plating method.