Methods of forming a contact structure in a semiconductor device include providing a semiconductor substrate including active regions and word lines crossing the active regions. A first interlayer dielectric layer is formed on the semiconductor substrate. Direct contact plugs are formed extending through the first interlayer dielectric layer to contact selected ones of the active regions. Bit line structures are formed on the first interlayer dielectric layer and crossing the word lines that are coupled to the selected ones of the active regions by the direct contact plugs. A second interlayer dielectric layer is formed on the semiconductor substrate including the bit line structures. Barrier patterns are formed extending in parallel with bit line structures and into the second interlayer dielectric layer. Mask patterns are formed overlying an entirety of top surfaces of the direct contact plugs on the second interlayer dielectric layer and the bit line structures. The second and first interlayer dielectric layers are is etched using the mask patterns, the barrier patterns and the bit line structures as an etching mask to form buried contact holes and buried contact plugs are formed in the buried contact holes.