To resolve the conventional problems where generations of cracks and deformations cannot be suppressed sufficiently and increases in junction layers, thermal resistances, and manufacturing processes are caused by using intermediate relaxation materials.

There existed problems where when mounting on a housing the parts having various thermal expansion coefficients, cracks are generated in the parts and junction portions, and the parts and the housing are deformed, due to thermal stresses generated by the differences of the thermal expansion coefficients existent between the parts and the housing. Conventionally, methods are adopted which suppress the thermal tresses, by using the junction materials having small elasticities and by sandwiching between the parts and the housing the relaxation materials, whose elasticities are their intermediate ones. Here, for resolving the still left conventional problems, a carbon-fiber reinforced aluminum material, whose carbon-fiber density is varied continuously in its thickness direction, is used as the material for housings 1a-1c. By respectively adapting the heights of the mounted parts 2a, 2b for their thermal expansion coefficients, the expansion coefficients of the parts 2a, 2b and the housings 1a-1c are matched with each other so as to relax their thermal stresses. By adjusting to down to a range of 35%-0% the carbon-fiber content of the aluminum material, the slope of the temperature characteristic of its linear expansion coefficient can be varied within the range of 4-24 ppm/°C.