Three-dimensional memory device

A three-dimensional memory device, comprising:

• a substrate having an array area and a staircase area, wherein the substrate comprises a lower portion and an upper portion;
• a first multi-layered stack disposed on the substrate, wherein the first multi-layered stack comprises a plurality of first insulating layers and a plurality of conductive layers arranged alternately;
• a plurality of vertical channel pillars disposed in the first multi-layered stack and the array area of the substrate;
• a barrier structure disposed in the first multi-layered stack and the staircase area of the substrate, wherein the barrier structure penetrates the first multi-layered stack and extends into the upper portion of the substrate;
• and
• a first slit structure and a second slit structure disposed in the first multi-layered stack and the substrate along a first direction, wherein the second slit structure is in contact with the barrier structure, and the first slit structure and the second slit structure collectively separate the vertical channel pillars in a second direction that is different from the first direction.