The method may include forming a plurality of fins on a substrate with first and second regions, forming a photoresist pattern to expose the fins of the first region, forming a material layer to cover the fins of first region and the photoresist pattern, chemically reacting the photoresist pattern the material layer to form a supplemental film on a side surface of the photoresist pattern, performing an ion implantation process using the photoresist pattern and the supplemental film as a ion injection mask to form impurity layers in the fins of the first region.