A power semiconductor module having an integral circuit board with a metal substrate electrode, an insulation substrate and a heat sink joined is disclosed. A SiC semiconductor power device is joined to a top of the metal substrate electrode of the circuit board. A difference in average coefficients of thermal expansion between constituent materials of the circuit board in a temperature range from room to joining time temperatures is 2.0 ppm/.degree. C. or less, and a difference in expansion, produced by a difference between a lowest operating temperature and a joining temperature, of the circuit-board constituent materials is 2,000 ppm or less.