A method of forming patterns of a semiconductor device includes forming a hard mask layer and a first sacrificial layer over a first region and a second region of a semiconductor substrate, etching the first sacrificial layer to form a first sacrificial pattern having a first width in the first region and second sacrificial patterns having a second width in the second region, wherein the second width is narrower than the first width, forming a first spacer surrounding sidewalls of the first sacrificial pattern and a second spacer surrounding sidewalls of the second sacrificial patterns, removing the first and the second sacrificial patterns; and etching the first and second spacers.