A module is provided that has high reliability in the junction between a ceramic circuit board and a heat sink, undergoes small changes in shape and warp of a module structure comprising a ceramic circuit board and a metal heat sink event under a temperature history during power module assembly and power module actual use, eliminates an unfavorableness during power module assembly, and maintains high reliability over a long period of time. A module structure characterized in that in a module member formed by bonding the ceramic circuit board to the metal heat sink via a metal plate (A) the main component of which is aluminum, the metal plate (A) has a thickness of 400 .mu.m or more and 1,200 .mu.m or less.