The present invention enables improvement of bonding reliability of the conductive adhesive interposed between a semiconductor chip and a die pad portion. Provided is a semiconductor device, in which a silicon chip is mounted over the die pad portion integrally formed with a drain lead, has a source pad over the main surface and a drain electrode of a power MOSFET over the back side, and is bonded onto the die pad portion via an Ag paste. In the device, a source lead and the source pad are electrically coupled via an Al ribbon. Over the back surface of the silicon chip, an Ag nanoparticle coated film is formed, while another Ag nanoparticle coated film is formed over the die pad portion and lead (drain lead and source lead).