A semiconductor device includes a wiring board, a first semiconductor chip (e.g. DRAM) that is flip-chip connected on the wiring board, a second semiconductor chip (e.g. DRAM) that is of the same type as the first semiconductor chip and is mounted face up on the first semiconductor chip such that the orientation of the arrangement of the pads is at 90° from that of the first semiconductor chip, a third semiconductor chip (e.g. microcomputer chip) disposed on the second semiconductor chip, wires, and a sealing medium. The wiring board has a plurality of common wiring patterns for electrically connecting first electrodes for the first semiconductor chip and second electrodes for the second semiconductor chip. The common wiring patterns can be disposed without crossing on the surface wire layer of the wiring board.