In a method of forming a capacitor, a first mold layer pattern including a first insulating material may be formed on a substrate. The first mold layer pattern may have a trench. A supporting layer including a second insulating material may be formed in the trench. The second insulating material may have an etching selectivity with respect to the first insulating material. A second mold layer may be formed on the first mold layer pattern and the supporting layer pattern. A lower electrode may be formed through the second mold layer and the first mold layer pattern. The lower electrode may make contact with a sidewall of the supporting layer pattern. The first mold layer pattern and the second mold layer may be removed. A dielectric layer and an upper electrode may be formed on the lower electrode and the supporting layer pattern.