A module which has a 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 metallic heat sink even under a temperature history during power module assembly and power module actual use, eliminates an unfavorableness during power module assembly, and maintains a high reliability over a long period. A module structure is characterized in that a module member formed by bonding a ceramic circuit board to the metallic heat sink via a metal plate A the main component of which is aluminum has a thickness of the metal plate A of not less than 400mum and not more than 1200mum.
