For a semiconductor device having copper wiring, an exemplary method according to an embodiment of the present invention may include forming a first insulation layer on a silicon substrate having a transistor thereon; forming a contact hole by etching the first insulation layer; forming a metal plug so as to fill the contact hole; forming a second insulation layer on the metal plug; forming a trench exposing an upper surface of the metal plug by partially removing the second insulation layer; sputter-etching an interior wall and bottom surface of the trench with a plasma; and forming a copper line layer so as to fill the sputter-etched trench. According to this method, electrical contact between a metal plug and a copper line layer may be maintained or improved prevented by reducing or removing by-products on the metal plug using the sputter-etching process.