Various embodiments disclose a 3D memory device, including a substrate; a plurality of conductor layers disposed on the substrate; a plurality of NAND strings disposed on the substrate; and a plurality of slit structures disposed on the substrate. The plurality of NAND strings can be arranged perpendicular to the substrate and in a hexagonal lattice orientation including a plurality of hexagons, and each hexagon including three pairs of sides with a first pair perpendicular to a first direction and parallel to a second direction. The second direction is perpendicular to the first direction. The plurality of slit structures can extend in the first direction.