In a semiconductor device having a WCSP type construction package, to increase inductance without increasing further an area conventionally occupied by a coil. A pseudo-post part 27 comprising a magnetic body is extended in a direction perpendicular to a main surface 12a of a semiconductor chip 12, on a second insulating layer 21 of a WCSP 10. A first conductive part 15a and a second conductive part 15b constructed as square frames are respectively provided so as to surround the pseudo-post part, on respective top surfaces of a second insulation layer and a third insulating layer 22 which are separated parallel to each other, in an extension direction of the pseudo-post part. A coil 100 being a substantially spiral shape conductive path is formed from, the first conductive part, the second conductive part, and a connection part 26 which electrically connects the one ends of the first and second conductive parts.