In a method of forming a dual damascene pattern of a semiconductor device, horns that occur while forming a trench constituting the dual damascene pattern are removed in an intermediate process of forming the trench. Thus, the source of particles, which occur due to the horns in a cleaning process performed after the dual damascene pattern is formed, may be removed. Accordingly, an increase of contact resistance due to particles may be prevented, and a reduction in the yield of semiconductor devices may also be improved.