A semiconductor device includes a semiconductor substrate having a cell region and a dummy region surrounding the cell region, a plurality of memory pillar structures, and a supporting layer. The memory pillar structures are on the cell region. The supporting layer is over the semiconductor substrate, interconnecting the memory pillar structures, and having a plurality of first and second opening patterns on the cell region. A first number of the memory pillar structures surround each of the first opening patterns, and a second number of the memory pillar structures surround each of the second opening patterns. The first opening patterns are different from the second opening patterns, the first number is different from the second number, and at least one of the first opening patterns and at least one of the second opening patterns are on a central portion of the cell region.