A semiconductor memory device includes a substrate having a first region, a second region, and a third region main separation regions extending in the first direction and apart from each other in a second direction, first auxiliary separation regions extending in the first direction and spaced apart from each other in the second direction, and second auxiliary separation regions extending in the first direction and spaced apart from each other in the second direction. The first auxiliary separation regions are at a first pitch in the second direction between the main separation regions, the second auxiliary separation regions are disposed at a second pitch, smaller than the first pitch in the second direction between the main separation regions, and the first auxiliary separation regions and the second auxiliary separation regions are shifted from each other in the second direction.