A transistor is formed on a bonded SOI substrate. A collector electrode is connected to the peripheral sides of the collector areas on the insulator. A first insulator of isolation is formed on the peripheral side of the collector electrode. A base electrode is connected to a base area on the first insulator of isolation. Second insulators of isolation are formed on the peripheral side of a base electrode, and emitter electrode is connected to an emitter area by the second insulators of isolation. The connections between the collector electrode and the collector areas, between the base electrode and the base area, and between the emitter electrode and the emitter area are made under the emitter electrode, so the occupation area is small.