Provided is a memory device, including a plurality of gate pillar structures and a plurality of dielectric pillars. The gate pillar structures and the dielectric pillars are arranged alternately and separately along a first direction, and are arranged alternately and contact each other along a second direction. In addition, the gate pillar structures and the dielectric pillars are embedded in a stack layer along a third direction, thereby dividing the stack layer into a plurality of stack structures. A sidewall of each of the dielectric pillars in the second direction and a sidewall of the adjacent gate pillar structure in the second direction are not coplanar.