First gate lines are formed on a substrate. An insulation layer is formed on the substrate and the first gate lines. The insulation layer disposed between the first gate lines is selectively etched, to thereby form first openings. Landing plugs are buried into the first openings. The insulation layer disposed on the first gate lines is etched until upper portions of the first gate lines are exposed, thereby obtaining second openings. Second gate lines are formed inside the second openings.