A method of fabricating a semiconductor integrated circuit device, including providing a semiconductor substrate, sequentially forming an etching target layer and a hard mask layer on the semiconductor substrate, forming first etch masks on the hard mask layer, the first etch masks including a plurality of first line patterns spaced apart from one another at a first pitch and extending in a first direction, forming first hard mask patterns by etching the hard mask layer using the first etch masks, forming second etch masks on the first hard mask patterns, the second etch masks including a plurality of second line patterns spaced apart from one another at a second pitch and extending in a second direction different from the first direction, forming second hard mask patterns by etching the first hard mask patterns using the second etch masks, forming spacers on sidewalls of the second hard mask patterns, and patterning the etching target layer using the second hard mask patterns having the spacers.