Method of manufacturing semiconductor device

A method of manufacturing a semiconductor device, the method comprising:

• a step (a) of manufacturing a semiconductor module by sealing, with a mold resin, a first metal plate, an insulating layer bonded to a lower surface of the first metal plate, a second metal plate bonded to a lower surface of the insulating layer, and a semiconductor element mounted on an upper surface of the first metal plate with a first bonding member between the semiconductor element and the first metal plate in a state in which a lower surface of the second metal plate is exposed;
• and
• a step (b) of mounting the semiconductor module on a metal base plate by bonding the lower surface of the second metal plate to an upper surface of the metal base plate by a second bonding member having a melting point lower than a melting point of the first bonding member, wherein
• the step (b) includes steps of disposing the semiconductor module on the upper surface of the metal base plate with the second bonding member between the semiconductor module and the metal base plate, heating the metal base plate, the second bonding member, and the semiconductor module to melt the second bonding member, and then cooling the metal base plate, the second bonding member, and the semiconductor module to cure the second bonding member, and
• during the cooling of the metal base plate, the second bonding member, and the semiconductor module, a difference between an upper surface temperature of the metal base plate and a lower surface temperature of the first metal plate at a solid phase line of the second bonding member is 5° C. or less.