A method of forming fine patterns of a semiconductor device, in which a plurality of conductive lines formed in a cell array region are integrally formed with contact pads for connecting the conductive lines to a peripheral circuit. In this method, a plurality of mold mask patterns, each including a first portion extending in a first direction and a second portion which is integrally formed with the first portion and extends in a second direction, are formed within a cell block on a substrate comprising a film which is to be etched. A first mask layer covering sidewalls and an upper surface of each of the plurality of mold mask patterns is formed on the substrate. First mask patterns are formed by partially removing the first mask layer so that a first area of the first mask layer remains and a second area of the first mask layer is removed. The first area of the first mask layer covers sidewalls of adjacent mold mask patterns from among the plurality of mold mask patterns by being located between the adjacent mold mask patterns, and the second area of the first mask layer covers portions of the sidewalls of the plurality of mold mask patterns, the portions corresponding to an outermost sidewall of a mold mask pattern block.