A semiconductor device comprising a pair of heat sinks and methods for their preparation

A semiconductor device includes a heating element (10); a first heat sink (30) which is arranged on one side of the heating element (10); a second heat sink (40) which is arranged on the other side of the heating element (10); and a resin mass (80) for casting the heating element (10) and the first and second heat sinks (30, 40). The first heat sink (30) includes a first heat radiation surface (30a) which is disposed opposite to the heating element (10) and free from the resin composition (80). The second heat sink (40) includes a second heat radiation surface (40a) which is disposed opposite to the heating element (10) and free from the resin composition (80). The first and second heat radiation surface (30a, 40a) have equal to or less than 0.2 mm from each other a degree of parallelism.