A method for manufacturing a semiconductor device includes forming an insulation film over a semiconductor substrate having a conduction layer; forming a trench pattern over the insulation film; etching an upper portion of the insulation film by using the trench pattern as a mask to form a trench; removing the trench pattern; forming a spacer film over the insulation film having the trench; etching the space film to form a spacer by using a blanket etching process, the spacer remaining over an edge of an inner portion of the trench; etching the insulation film to form a via hole by using as a mask the spacer; completely removing the spacer; forming a barrier film over sidewalls of the trench and the via hole; and forming a metal line with which fills inner portions of the trench and the via hole.