The object of the present invention is to reduce parasitic inductance of a main circuit in a power supply circuit. The present invention provides a non-insulated 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 DC-DC converter, the power MOS.cndot.FET for the high-side switch is formed by a p channel vertical MOS.cndot.FET, and the power MOS.cndot.FET for the low-side switch is formed by an n channel vertical MOS.cndot.FET. Thus, a semiconductor chip formed with the power MOS.cndot.FET for the high-side switch and a semiconductor chip formed with the power MOS.cndot.FET for the low-side switch are mounted over the same die pad and electrically connected to each other through the die pad.