A metal line is fabricated in a semiconductor device by a method including: forming an etch stop layer on a substrate; forming an interlayer insulating layer on the etch stop layer, the interlayer insulating layer including dual damascene patterns, each respectively having a trench and a via contact hole; forming a barrier metal layer and a line metal layer on the interlayer insulating layer and in the dual damascene patterns; forming an anti-oxidation layer on above the line metal layer; and forming a metal line in the dual damascene patterns by planarizing an entire surface of the anti-oxidation layer.