A semiconductor composite device is provided that includes a voltage regulator, a package board, and a load, and converts an input DC voltage into a different DC voltage to supply the converted DC voltage to the load. The VR includes a semiconductor active element. The package board includes a C layer in which a capacitor is formed, and an L layer in which an inductor is formed. A plurality of through holes penetrate the C layer and the L layer in a direction perpendicular to the mounting face in the package board. The capacitor is connected to the load through the through hole. The inductor is connected to the load through the through hole and to the VR through the through hole.