A semiconductor device including a substrate that includes a cell array region and a peripheral circuit region; a cell transistor on the cell array region of the substrate; a peripheral transistor on the peripheral circuit region of the substrate; a first interconnection layer connected to the cell transistor; a second interconnection layer connected to the peripheral transistor; an interlayer dielectric layer covering the first interconnection layer; and a blocking layer spaced apart from the first interconnection layer, the blocking layer covering a top surface and a sidewall of the second interconnection layer.