Connection reliability in electrode portions of a semiconductor module is improved. A semiconductor wafer is prepared where a plurality of semiconductor substrates each having an electrode and a protective film at the surface is formed in a matrix shape. Next, at the surface of the semiconductor wafer (semiconductor substrate) a insulation layer is held between the semiconductor substrate and a copper sheet (metal sheet) formed integrally with a bump containing a plastic region on a tip part. With the insulating held between them, the semiconductor substrate, the insulating layer and the copper sheet are press-formed by a press machine into a single block. The bump penetrates the insulating layer, and the plastic region on the tip part is plastic deformed at a contact surface with an electrode, so that the bump and the electrode are electrically connected together.