A method includes forming a first etch target layer and a first mask layer on a substrate. Sacrificial patterns extending in a first direction are formed on the first mask layer in a second direction. Spacers are formed on sidewalls of the sacrificial patterns. After removing the sacrificial patterns, the first mask layer is etched using the spacers as an etching mask to form first masks. Second masks are formed on sidewalls of each first mask to define a third masks including each first mask and the second masks on sidewalls of each first mask. The first etch target layer is etched using the first and third masks as an etching mask to form first and second patterns in the first and second regions, respectively. Each first pattern has a first width, and each second pattern has a second width greater than the first width.