Patent ID: 7554114

Claim:
A semiconductor device comprising: at least one semiconductor element mounted on a thermally conductive substrate; electrical connecting portions for electrically connecting the semiconductor elements to external devices; a first synthetic high-molecular compound mainly comprised of polymethylsilsesquioxane and polymethylphenylsiloxane which covers the semiconductor elements and at least part of the electrical connecting portions and which contains a compound having a three-dimensional steric structure formed by linking plural third organosilicon polymers with covalent bonds resulting from an addition reaction, said third organosilicon polymers being formed by linking at least one first organosilicon polymer having a crosslinked structure using siloxane with at least one second organosilicon polymer having a linear linked structure using siloxane through siloxane bonds; a case of a hard resin provided on the substrate so as to house the semiconductor elements and the electrical connecting portions covered with said first synthetic high-molecular compound; a second synthetic high-molecular compound which is mainly comprised of polyphenylsilses-quioxane and polydimethylsiloxane, and which fills a remaining space within said case such that said second high-molecular comuound acts as a buffer that prevents the semiconductor elements from vibrating due to a mechanical shock applied to the semiconductor device: the polydimethylsiloxane of said second synthetic high-molecular compound having a longer polymeric molecular structure than the polymethylphenylsiloxane of said first synthetic high-molecular compound; and external connecting terminals which are connected to the electrical connecting portions and which lead outside the case.