A plurality of LSI chips (1) are stacked on an interposer (2). Signal coils (1b) for signal transmission are formed on the circuit formation surfaces of LSI chips (1) that are formed using silicon substrates (1a). The signal coils (1b) connect to circuits formed in the LAI chips (1). Through-holes (1d) are formed in the centers of the signal coils (1b) of the silicon substrate (1a). Signal coils (2c) connected to solder balls (5) by way of through-conductors (2d) are formed on the interposer (2). Magnetic pins (3) that are composed of a magnetic material are inserted in the centers of the signal coils (1b and 2c).