A semiconductor device in accordance with the present invention includes IC chips (semiconductor elements) (2, 3, 4) having solder bumps (24) (projecting electrodes) formed on electrode pads, and a first wiring board (1) having connection terminals (7) to which the respective solder bumps (24) of the IC chips (2, 3, 4) are connected, external connection terminals (8) for connection to an external apparatus, and conductor wires (9) provided in respective groove portions formed in a board surface and connected to the respective connection terminals (7). In spite of the reduced pitch of the conductor wires (9), the presence of the groove portions enables an increase in cross section, allowing a reduction in wiring resistance.