A method of fabricating an integrated circuit device includes forming first and second preliminary mask structures on a hard mask layer in respective first and second regions of the substrate. Spacers are formed on opposing sidewalls of the first and second preliminary mask structures, and the first preliminary mask structure is selectively removed from between the spacers in the first region. The hard mask layer is etched using the spacers and the second preliminary mask structure as a mask to define a first mask pattern including the opposing sidewall spacers with a void therebetween in the first region and a second mask pattern including the opposing sidewall spacers and the second preliminary mask structure therebetween in the second region. An insulation layer is patterned using the first and second mask patterns as respective masks to define a first trench in the first region and a second trench in the second region having a greater width than the first trench, and first and second conductive patterns are formed in the first and second trenches.