A memory device and an electronic system, the memory device including a substrate; a ground selection line on the substrate, a cutting portion cutting the ground selection line; a first insulation layer and a first word line stacked immediately above the ground selection line; and second insulation layers and second word lines alternately stacked on the first word line, wherein the first word line includes a first portion laterally offset from the cutting portion and a second portion overlying the cutting portion, the first portion of the first word line has a first thickness, and the second portion of the first word line has a second thickness less than the first thickness.