Methods of fabricating a semiconductor device are provided. Methods of forming a finer pattern of a semiconductor device using a buffer layer for retarding, or preventing, bridge formation between patterns in the formation of a finer pattern below resolution limits of a photolithography process by double patterning are also provided. A first hard mask layer and/or a second hard mask layer may be formed on a layer of a substrate to be etched. A first etch mask pattern of a first pitch may be formed on the second hard mask layer. After a buffer layer is formed on the overall surface of the substrate, a second etch mask pattern of a second pitch may be formed thereon in a region between the first etch mask pattern. The buffer layer may be anisotropically etched using the second etch mask pattern as an etch mask, forming a buffer layer pattern. The second hard mask layer may be anisotropically etched using the first etch mask pattern and/or the buffer layer pattern as etch masks, forming a second hard mask pattern. The first hard mask layer may be anisotropically etched using the second hard mask pattern as an etch mask, forming a first hard mask pattern. The etched layer may be anisotropically etched using the first hard mask pattern as an etch mask.