A patterning method has a mask layer and undoped patterns sequentially formed on a target layer. A doping process is performed to surfaces of the undoped patterns to form doped patterns from the surfaces of the undoped patterns. A material is filled in the gaps between the doped patterns. A portion of the doped patterns are then removed to expose the top surfaces of the remaining undoped patterns. The material and the exposed undoped patterns are removed. A portion of the mask layer is removed using the remaining doped patterns as a mask to form a first pattern on the mask layer. A portion of the target layer is removed using the mask layer having the first pattern thereon as a mask so as to form on the target layer a second pattern complementary to the first pattern.