Contact structures for three-dimensional memory device

A method for forming a three-dimensional memory structure, comprising:

• disposing a dielectric film stack on a substrate, wherein the dielectric film stack comprises a plurality of alternating dielectric layer pairs, each alternating dielectric layer pair comprising a first dielectric layer and a second dielectric layer different from the first dielectric layer;
• forming a dielectric staircase in the dielectric film stack, wherein the dielectric staircase comprises a plurality of dielectric staircase steps, each dielectric staircase step comprising two or more alternating dielectric layer pairs;
• disposing a first insulating layer on the dielectric staircase;
• forming a plurality of memory strings in the dielectric film stack;
• replacing the second dielectric layers with conductive layers to form a staircase structure with a plurality of staircase steps, wherein each staircase step comprises two or more conductive and dielectric layer pairs, each conductive and dielectric layer pair comprising a conductive layer and the first dielectric layer;
• and
• forming a plurality of coaxial contact structures on the staircase structure.