A semiconductor device includes a submount; a semiconductor laser mounted on the submount via solder in a junction-down manner. The semiconductor laser includes a semiconductor substrate, a semiconductor laminated structure containing a p-n junction, on the semiconductor substrate, and an electrode on the semiconductor laminated structure and joined to the submount via the solder. A high-melting-point metal or dielectric film is located between the submount and the semiconductor laminated structure and surrounds the electrode.