A semiconductor device includes a semiconductor substrate, a first metal film on a back surface of the semiconductor substrate, a second metal film on the first metal film, and a third metal film on the second metal film. The first metal film forms an alloy with a solder. The second metal film causes isothermal solidification of the solder. The third metal film improves solder wetting properties or inhibits oxidation. Further, in a method for die-bonding a semiconductor device, a specific metal is diffused into a solder, when the solder melts, to transform the solder into a high melting point alloy, thereby causing isothermal solidification of the solder. The specific metal is different from the metal of the solder.