Provided are a method of forming patterns for a semiconductor device in which a pattern density is doubled by performing double patterning in a part of a device region while patterns having different widths are being simultaneously formed, and a semiconductor device having a structure to which the method is easily applicable. The semiconductor device includes a plurality of line patterns extending parallel to each other in a first direction. A plurality of first line patterns are alternately selected in a second direction from among the plurality of line patterns and each have a first end existing near the first side. A plurality of second line patterns are alternately selected in the second direction from among the plurality of line patterns and each having a second end existing near the first side. The first line patterns alternate with the second line patterns and the first end of each first line pattern is farther from the first side than the second end of each second line pattern.