A method of forming patterns of a semiconductor device, including partially etching an upper portion of a substrate to form first preliminary active patterns and a first trench, each of the first preliminary active patterns having a first width, and the first trench having a second width of about 2 to 3 times the first width; forming an insulating spacer on each sidewall of the first trench to form a second trench having the first width; forming a second preliminary active pattern in the second trench, the second preliminary active pattern having the first width; partially etching the first and second preliminary active patterns to form a plurality of first active patterns and a plurality of second active patterns and an opening between the plurality of first and second active patterns; and forming an insulation pattern to fill the opening.