The inventive concepts provide methods of forming a semiconductor device. The method includes forming a neutral layer having a photosensitive property and a reflow property on an anti-reflective coating layer, performing an exposure process and a development process on the neutral layer to form a preliminary neutral pattern at least partially exposing the anti-reflective coating layer, heating the preliminary neutral pattern to form a neutral pattern, forming a block copolymer layer on the neutral pattern, and heating the block copolymer layer to form a block copolymer pattern. The block copolymer pattern includes a first pattern disposed on the anti-reflective coating layer exposed by the neutral pattern, and a second pattern disposed on the neutral pattern and chemically bonded to the first pattern.