The present invention provides a non-insulated type DC-DC converter having a circuit in which a power MOS.cndot.FET for a high side switch and a power MOS.cndot.FET for a low side switch are connected in series. In the non-insulated type DC-DC converter, the power transistor for the high side switch, the power transistor for the low side switch, and driver circuits that drive these are respectively constituted by different semiconductor chips. The three semiconductor chips are accommodated in one package, and the semiconductor chip including the power transistor for the high side switch, and the semiconductor chip including the driver circuits are disposed so as to approach each other.