A power supply capable of reducing loss of large current and high frequency. In an MCM for power supply in which a high-side power MOSFET chip, a low-side power MOSFET chip and a driver IC chip driving them are sealed in one sealing material (a capsulating insulation resin), a wiring length of a wiring DL connecting an output terminal of the driver IC chip to a gate terminal of the low-side power MOSFET chip or a source terminal is made shorter than a wiring length of a wiring DH connecting the output terminal of the driver IC chip to a gate terminal of the high-side power MOSFET chip or a source terminal. Further, the number of the wiring DL is made larger than the number of the wiring DH.