A semiconductor device includes a substrate and memory cell arrays arranged on the substrate in a first direction and second direction. The first direction and second direction are parallel to a top surface of the substrate and intersect each other. The memory cell arrays include a plurality of memory cells. A cell dummy pattern on the substrate is arranged between the memory cell arrays in at least one of the first direction and second direction and extends along a side of the memory cell arrays. A cell conductive pattern is included on the substrate. A cell contact plug is configured to connect the cell dummy pattern and the cell conductive pattern. The cell contact plug is arranged between the cell dummy pattern and the cell conductive pattern in a third direction that is perpendicular to the first direction and the second direction.