Ceramic-metal composite substrate and method for producing the same

A method for producing a ceramic-metal composite substrate, which comprises integrally bonding together a ceramic base member, copper based metal members and a constraining member to be bonded to one of said copper based metal members, wherein the improvement comprises:

• forming a substrate member by bringing first and second copper based metal members into close contact with both surfaces of said ceramic base member each through a thin film layer which is formed of an active metal, said first and second copper based metal members and said active metal layers subsequently forming an alloy when heated, and further bringing a third copper member for mounting semiconductor elements into close contact with a non-contacted surface of any one of said first and second copper members through said constraining member;
• and heating the thus formed combined layers in an atmosphere which is essentially inert with said active metal, to a temperature ranging from the melting point of said alloy to a temperature below the melting point of said first and second copper members, while applying a pressing force to the combined members in the direction of the thickness of the composite substrate, thereby achieving integral bonding of the members.