A semiconductor device includes a plurality of line patterns including at least two continuous line repetition units having, as one of the line repetition unit, four line patterns continuously arranged in a first direction and having variable widths based on location. To form the plurality of line patterns including the at least two continuous line repetition units, a plurality of reference patterns are formed repeatedly at a uniform reference pitch on a feature layer. A plurality of first spacers covering both side walls of each of the plurality of reference patterns are formed. A plurality of second spacers covering both side walls of each of the plurality of first spacers are formed by removing the plurality of reference patterns. The feature layer is etched using the plurality of second spacers as an etch mask by removing the plurality of first spacers.