The present invention enhances the reliability of a semiconductor device. The semiconductor device includes a package substrate having a dry resist film which covers some conductive portions out of a plurality of conductive portions formed on a main surface and a back surface and is formed of a film, a semiconductor chip which is mounted over the package substrate, conductive wires which electrically connect the semiconductor chip with the package substrate, a die-bonding film which is arranged between the main surface of the package substrate and the semiconductor chip, a plurality of solder bumps which are formed on the back surface of the package substrate, and a sealing body which is made of resin. By forming the dry resist film made of a film on the main surface and the back surface of the package substrate, it is possible to suppress the warping of the package substrate and hence, the occurrence of package cracks at the time of reflow mounting can be prevented thus enhancing the reliability of the semiconductor device.