A method of forming fine patterns of a semiconductor device includes forming a plurality of first mask patterns on a substrate such that the plurality of first mask patterns are separated from one another by a space located therebetween, in a direction parallel to a main surface of the substrate, forming a plurality of capping films formed of a first material having a first solubility in a solvent on sidewalls and a top surface of the plurality of first mask patterns. The method further includes forming a second mask layer formed of a second material having a second solubility in the solvent, which is less than the first solubility, so as to fill the space located between the plurality of first mask patterns, and forming a plurality of second mask patterns corresponding to residual portions of the second mask layer which remain in the space located between the plurality of first mask patterns, after removing the plurality of capping films and a portion of the second mask layer using the solvent.