Provided are a method of fabricating a semiconductor device unconstrained by optical limit and an apparatus of fabricating the semiconductor device. The method includes: forming an etch target layer on a substrate; forming a hard mask layer on the etch target layer; forming first mask patterns on the hard mask layer; forming first spacers on sidewalls of the first mask patterns; forming hard mask patterns having an opening by using the first mask patterns and the first spacers as a mask to etch the hard mask layer; aligning second mask patterns on the hard mask patterns to fill the opening; forming second spacers on sidewalls of the second mask patterns; forming fine mask patterns by using the second mask patterns and the second spacers as a mask to etch the hard mask patterns; and forming fine patterns by using the fine mask patterns as a mask to etch the etch target layer.