Methods of fabricating a semiconductor device are provided. The methods may include forming a stopper layer on a target layer including a cell area and an edge area, forming a hard mask including first upper openings and dam trench on the stopper layer, forming opening spacers on inner walls of the first upper openings and a dam pattern in the dam trench, removing the stopper layer exposed in the first upper openings to form first lower openings, forming pillar patterns in the first lower openings and the first upper openings and an eaves pattern on the dam pattern, removing the hard mask in the cell area, forming a first polymer block between the pillar patterns including second upper openings, etching the stopper layer exposed in the second upper openings to form second lower openings, and removing the first polymer block, the pillar patterns, the dam pattern and the eaves pattern.