A semiconductor module of the present invention comprises a first conductive layer (film) and a second conductive layer (film) which are separately formed on the main surface of a packed substrate, a thermal diffusion plate connected by solder to the upper surface of the first conductive layer, a semiconductor element connected by solder to the upper surface of the thermal diffusion plate, and a lead having one end connected by solder to the second conductive layer and the other end connected by solder to the semiconductor element, wherein the outer periphery of the connected region where the semiconductor element is connected by solder to the upper surface of the thermal diffusion plate is formed with protrusion parts protruding up from the connecting region and a turning of the semiconductor element in the upper surface of the thermal diffusion plate in the solder connecting process is suppressed by the protrusion parts.