A method for forming copper wirings in a semiconductor device may include depositing a lower insulating film over a semiconductor substrate; forming vias in the lower insulating film; depositing tungsten over the entire surface of upper portion of the lower insulating film so that the vias are gap-filled with the tungsten; forming tungsten plugs by performing a tungsten chemical mechanical polishing process to remove excess tungsten deposited over the upper portion of the lower insulating film; removing the tungsten remaining over the upper portion of the lower insulating film by performing a tungsten etchback process; depositing an upper insulating film over the upper portion of the lower insulating film; exposing upper portions of the tungsten plugs by forming trenches on the upper insulating film; depositing copper over the entire surface of the upper insulating film so that the trenches are gap-filled with the copper; and planarizing the copper over the upper portion of the trenches.