A method of forming fine line patterns of semiconductor devices includes: forming a plurality of lower linear core structures on at least one lower hard mask layer disposed on a target layer; forming a spacer layer on the hard mask layer to cover the lower linear core structures; forming an upper hard mask layer on the spacer layer; thinning the upper hard mask layer to expose potions of the spacer layer; and removing the exposed portions of the spacer layer to form a plurality of line patterns on the lower hard mask layer.