A semiconductor device includes a semiconductor pattern on a semiconductor substrate, a three-dimensional memory array on the semiconductor pattern, and a peripheral interconnection structure between the semiconductor pattern and the semiconductor substrate. The peripheral interconnection structure includes an upper interconnection structure on a lower interconnection structure. The upper interconnection structure includes an upper interconnection and an upper barrier layer. The lower interconnection structure includes a lower interconnection and a lower barrier layer. The upper barrier layer is under a bottom surface of the upper interconnection and does not cover side surfaces of the upper interconnection. The lower barrier layer is under a bottom surface of the lower interconnection and covers side surfaces of the lower interconnection.