A method for producing a semiconductor device by directly bonding silver oxide or silver (520; 620; 720) provided on a surface of a base (500; 600; 700) and silver oxide or silver (140; 240; 340) provided on a surface of a semiconductor element (100; 200; 300), at least one of the surface of the base (500; 600; 700) or the surface of the semiconductor element (100; 200; 300) being provided with silver oxide, the method comprising steps of: arranging the semiconductor element (100; 200; 300) on the base (500; 600; 700) such that the silver oxide or silver (140; 240; 340) provided on the surface of the semiconductor element (100; 200; 300) is in contact with the silver oxide or silver (520; 620; 720) provided on the surface of the base (500; 600; 700), temporarily bonding the semiconductor element (100; 200; 300) and the base (500; 600; 700) by applying a pressure or an ultrasonic vibration to the semiconductor element (100; 200; 300) or the base (500; 600; 700), and permanently bonding the semiconductor element (100; 200; 300) and the base (500; 600; 700) by applying heat having a temperature of 150 to 900°C to the semiconductor element (100; 200; 300) and the base (500; 600; 700); wherein the step of temporarily bonding and the step of permanently bonding may be performed simultaneously; wherein the base (500; 600; 700) is a lead frame or an organic or inorganic substrate furnished with a metallic wiring; wherein silver is provided on the surface of the base (500; 600; 700) and on the surface of the semiconductor element (100; 200; 300) by silver sputtering, silver vapour deposition or silver plating; and wherein the silver oxide (140; 240; 340; 520; 620; 720) is provided on at least one of the surface of the base (500; 600; 700) or the surface of the semiconductor element (100; 200; 300) by oxidizing the silver-coated surface on the entire base (500; 600; 700) or a part of the base (500; 600; 700) on which the semiconductor element (100; 200; 300) is to be mounted through oxygen plasma or UV-irradiation and/or by oxidizing the silver-coated surface of the semiconductor element (100; 200; 300) through oxygen plasma or UV-irradiation. arranging the semiconductor element (100; 200; 300) on the base (500; 600; 700) such that the silver oxide or silver (140; 240; 340) provided on the surface of the semiconductor element (100; 200; 300) is in contact with the silver oxide or silver (520; 620; 720) provided on the surface of the base (500; 600; 700), temporarily bonding the semiconductor element (100; 200; 300) and the base (500; 600; 700) by applying a pressure or an ultrasonic vibration to the semiconductor element (100; 200; 300) or the base (500; 600; 700), and permanently bonding the semiconductor element (100; 200; 300) and the base (500; 600; 700) by applying heat having a temperature of 150 to 900°C to the semiconductor element (100; 200; 300) and the base (500; 600; 700); wherein the step of temporarily bonding and the step of permanently bonding may be performed simultaneously; wherein the base (500; 600; 700) is a lead frame or an organic or inorganic substrate furnished with a metallic wiring; wherein silver is provided on the surface of the base (500; 600; 700) and on the surface of the semiconductor element (100; 200; 300) by silver sputtering, silver vapour deposition or silver plating; and wherein the silver oxide (140; 240; 340; 520; 620; 720) is provided on at least one of the surface of the base (500; 600; 700) or the surface of the semiconductor element (100; 200; 300) by oxidizing the silver-coated surface on the entire base (500; 600; 700) or a part of the base (500; 600; 700) on which the semiconductor element (100; 200; 300) is to be mounted through oxygen plasma or UV-irradiation and/or by oxidizing the silver-coated surface of the semiconductor element (100; 200; 300) through oxygen plasma or UV-irradiation.