A 3D semiconductor device includes an electrode structure has electrodes stacked on a substrate, semiconductor patterns penetrating the electrode structure, charge storing patterns interposed between the semiconductor patterns and the electrode structure, and blocking insulating patterns interposed between the charge storing patterns and the electrode structure. Each of the blocking insulating patterns surrounds the semiconductor patterns, and the charge storing patterns are horizontally spaced from each other and configured in such a way as to each be disposed around a respective one of the semiconductor patterns. Also, each of the charge storing patterns includes a plurality of horizontal segments, each interposed between vertically adjacent ones of the electrodes.