Staircase structures for three-dimensional memory device double-sided routing

A three-dimensional (3D) memory device, comprising:

• a substrate;
• a memory stack disposed on the substrate and comprising a plurality of conductor/dielectric layer pairs stacked alternatingly;
• and
• an array of memory strings each extending vertically through an inner region of the memory stack,
• wherein an outer region of the memory stack comprises a first staircase structure disposed on the substrate and a second staircase structure disposed on the substrate;
• first edges of the plurality of conductor/dielectric layer pairs in the first staircase structure along a vertical direction away from the substrate are staggered laterally away from the array of memory strings;
• and
• second edges of the plurality of conductor/dielectric layer pairs in the second staircase structure along the vertical direction away from the substrate are staggered laterally away from the array of memory strings.

A three-dimensional (3D) memory device, comprising:

• a substrate;
• a memory stack disposed above the substrate and comprising a plurality of conductor/dielectric layer pairs stacked alternatingly, wherein a length of each of the conductor/dielectric layer pairs decreases from a middle conductor/dielectric layer pair toward a top conductor/dielectric layer and a bottom conductor/dielectric layer pair, respectively;
• and
• an array of memory strings each extending vertically through the memory stack.