Patent ID: 7067857

Claim:
A semiconductor device, comprising: a semiconductor substrate, and at least one semiconductor element formed on the semiconductor substrate; wherein conductor layers connected respectively to desired areas of the semiconductor element are led out of the semiconductor element from a surface of the semiconductor substrate opposite to the other surface on which the semiconductor element is formed; wherein the semiconductor element is a heterojunction bipolar transistor and the conductor layers connected respectively to a base area, an emitter area and a collector area of the heterojunction bipolar transistor are led out from the surface of the semiconductor substrate opposite to the other surface on which the base, emitter and collector areas are formed; wherein the bottom surface of the semiconductor substrate has a first opening located so as to face the heterojunction bipolar transistor, and a second opening and a third opening both located so as not to face the heterojunction bipolar transistor; and wherein the conductor layers connected respectively to the base, emitter and collector areas of the heterojunction bipolar transistor are led out of the heterojunction bipolar transistor through the first, second and third openings.