FIG. 4 is a block diagram illustrating a memory block divided into a plurality of zones, according to an exemplary embodiment of the inventive concept. As illustrated in FIG. 4, the memory block BLKz may be divided into a plurality of zones Zone_1a to Zone_4a. Each of the remaining memory blocks BLK1 to BLKz-1 may be divided into a plurality of zones Zone_1a to Zone_4a in a manner similar to or the same as the memory block BLKz.

Referring to FIGS. 2, 3, and 4, the zones Zone_1a to Zone_4a may be determined based on the influence of the read disturbance. For example, the zones Zone_1a to Zone_4a may be determined according to a distance between the word lines WL1 to WL8 and the substrate SUB. First and second word lines WL1 and WL2 of which the distance from the substrate SUB is the shortest may be classified as a first zone Zone_1a.

On the basis of distances from the substrate SUB, third, fourth, and fifth word lines WL3, WL4, and WL5 may be classified as a second zone Zone_2a, sixth and seventh word lines WL6 and WL7 as a third zone Zone_3a, and an eighth word line WL8 as a fourth zone Zone_4a. For example, the read disturbance of a word line closer to the substrate SUB may be greater than the read disturbance of a word line distant from the substrate SUB.