Three dimensional semiconductor memory devices are provided. The three dimensional semiconductor memory device includes a first stacked structure and a second stacked structure sequentially stacked on a substrate. The first stacked structure includes first insulating patterns and first gate patterns which are alternately and repeatedly stacked on a substrate, and the second stacked structure includes second insulating patterns and second gate patterns which are alternately and repeatedly stacked on the first stacked structure. A plurality of first vertical active patterns penetrate the first stacked structure, and a plurality of second vertical active patterns penetrate the second stacked structure. The number of the first vertical active patterns is greater than the number of the second vertical active patterns.