A semiconductor module is provided which includes a semiconductor unit which is made by a resin mold. The resin mold has formed therein a coolant path through which a coolant flows to cool a semiconductor chip embedded in the resin mold. The resin mold also includes heat spreaders, and electric terminals embedded therein. Each of the heat spreaders has a fin heat sink exposed to the flow of the coolant. The fin heat sink is welded to a surface of each of the heat spreaders through an insulator, thus minimizing an electrical leakage from the heat spreader to the coolant.