Three-dimensional memory device and method for forming the same

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

• providing a substrate;
• forming a stack structure comprising a plurality of alternating conductive layers and dielectric layers on the substrate;
• performing an etching process to form a through-hole extending vertically through the stack structure, wherein a sidewall of the through-hole has a plurality of first recesses respectively at interfaces between the conductive layers and the dielectric layers;
• and
• forming a memory string structure in the through-hole, wherein the memory string structure comprises a storage layer covering along the sidewall of the through-hole and filling the first recesses and a conductive pillar on the storage layer and filling the through-hole.