In the semiconductor device, a control power MOSFET chip 2 is disposed on the input-side plate-like lead 5 , and the drain terminal DT 1 is formed on the rear surface of the chip 2 , and the source terminal ST 1 and gate terminal GT 1 are formed on the principal surface of the chip 2 , and the source terminal ST 1 is connected to the plate-like lead for source 12 . Furthermore, a synchronous power MOSFET chip 3 is disposed on the output-side plate-like lead 6 , and the drain terminal DT 2 is formed on the rear surface of the chip 3 and the output-side plate-like lead 6 is connected to the drain terminal DT 2 . Furthermore, source terminal ST 2 and gate terminal GT 2 are formed on the principal surface of the synchronous power MOSFET chip 3 , and the source terminal ST 2 is connected to the plate-like lead for source 13 . The plate-like leads for source 12 and 13 are exposed, and therefore, it is possible to increase the heat dissipation capability of the MCM 1.