A method of forming fine patterns of semiconductor device according to an example embodiment may include forming a plurality of multi-layered mask patterns by stacking first mask patterns and buffer mask patterns on an etch film to be etched on a substrate, forming, on the etch film, second mask patterns in spaces between the plurality of multi-layered mask patterns, removing the second mask patterns to expose upper surfaces of the first mask patterns, and forming the fine patterns by etching the etch film using the first and second mask patterns as an etch mask. This example embodiment may result in the formation of diverse dimensions at diverse pitches on a single substrate.