Abstract: The quality and reliability of a semiconductor device can be improved by eliminating a warp of a chip and performing a chip-stack. A wiring substrate, the first semiconductor chip connected via the first gold bump on the wiring substrate, the second semiconductor chip stacked via the second gold bump on the first semiconductor chip, and a sealing body are comprised. A first gold bump is connected to the wiring substrate, heating, and injection by pressure welding of the first gold bump is done under normal temperature after that at the hole-like electrode of the first semiconductor chip. Since injection by pressure welding of the second gold bump of the second semiconductor chip is done under normal temperature into the hole-like electrode of the first semiconductor chip and the second semiconductor chip is stacked, the chip-stack can be performed under normal temperature.