A semiconductor module includes a copper connector jointing an electrode formed on a top surface of a bare-chip transistor and a wiring pattern out of plural wiring patterns via a solder. The copper connector includes an electrode jointing portion jointed to the electrode of the bare-chip transistor and a substrate jointing portion arranged to face the electrode-jointing portion and jointed to the wiring pattern. The width W1 of the electrode jointing portion in a direction perpendicular to one direction is smaller than the width W2 of the substrate jointing portion in the direction perpendicular to the one direction.