Provided are three-dimensional semiconductor memory devices and methods of fabricating the same. The device may include an electrode structure extending in a first direction and including electrodes and insulating patterns which are alternately and repeatedly stacked on a substrate, and vertical active patterns penetrating the electrode structure. At least an uppermost electrode of the electrodes is divided into a plurality of physically isolated segments arranged in the first direction. The segments of the uppermost electrode are electrically connected to each other.