Of three chips (2A), (2B), and (2C) mounted on a main surface of a package substrate (1) in a multi-chip module (MCM), a chip (2A) with a DRAM formed thereon and a chip (2B) with a flash memory formed thereon are electrically connected to wiring lines (5) of the package substrate (1) through Au bumps (4), and a gap formed between main surfaces (lower surfaces) of the chips (2A), (2B) and a main surface of the package substrate (1) is filled with an under-fill resin (6). A chip (2C) with a high-speed microprocessor formed thereon is mounted over the two chips (2A) and (2B) and is electrically connected to bonding pads (9) of the package substrate (1) through Au wires (8).