SEMICONDUCTOR DEVICE

PROBLEM TO BE SOLVED: To satisfy guaranteed temperature of semiconductor chips in a semiconductor device, having a constitution where both faces of the semiconductor chips are electrically connected to a conductor member. SOLUTION: The guaranteed temperatures of the semiconductor chips 1 and 2 are set to Tjmax, and if the volume of an E heat sink 3 is set as V1 , the number of mols as M1 , mol specific heat as Cp1 , the specific gravity as g1 , the volume of a second conductor member 5 as V2 , the number of mols as M2 , mol specific heat as Cp2 , the specific gravity as g2 , the temperature of an outer cooling member 11 to be Ta and heat quantity added to the semiconductor chips 1 and 2 as Ja, the relation V1 >=M1 /(CP1 ×g1 )×Ja/(Tjmax-Ta)-Cp2 /M2 ×V2 ×g2 } is satisfied. By making the volume V1 of the E heat sink 3, which causes the heat of the semiconductor chips 1 and 2 to diffuse rapidly to be regulated, the guaranteed temperature Tjmax of the semiconductor chips 1 and 2 can be satisfied.