Abstract: A mask structure may include a first mask pattern and a second mask pattern formed on an object. When the object includes a first material, the first and the second mask patterns may include a second material and a third material, respectively. The second mask pattern may have at least two openings that expose portions of the object adjacent to sides of the first mask pattern. Because the mask structure has the first and the second mask patterns, desired structures, for example, recesses, trenches, contact holes or patterns may be more precisely formed on or through the object. For example, the first mask pattern may protect the object in an etching process for forming contact holes so that the contact holes may not be connected to each other, for example, when the contact holes have bar shapes or line shapes.