A semiconductor device wherein a semiconductor element made of Si or Si group material mounted on a substrate, the semiconductor element is mounted on the substrate and the semiconductor element is bonded to a silver bonding material via a oxide film formed on the semiconductor element. The bonding material comprising silver oxide particles having an average particle size of 1 nm to 50 nm and an organic reducing agent is used for bonding in air, which gives a high bonding strength to the oxide on the semiconductor element.