A method may include forming first hard mask patterns and second hard mask patterns extending in a first direction and repeatedly and alternately arranged on a lower layer, forming third mask patterns extending in a second direction perpendicular to the first direction on the first and second hard mask patterns, etching the first hard mask patterns using the third mask patterns to form first openings, forming filling patterns filling the first openings and gap regions between the third mask patterns, forming spacers on both sidewalls of each of the filling patterns, after removing the third mask patterns, and etching the second hard mask patterns using the filling patterns and the spacers to form second openings.