A semiconductor device includes a semiconductor substrate, a storage pad and a bit line pad on the semiconductor substrate, a first interlayer insulating layer covering the bit line pad and including a bit line contact hole having a width greater than a width of the bit line pad, a barrier insulating layer on sidewalls of the first interlayer insulating layer and upper portions of sidewalls of the bit line pad that are exposed by the bit line contact hole, a bit line plug in the bit line contact hole and on the barrier insulating layer; and a storage plug penetrating the first interlayer insulating layer and contacting the storage pad.