Three-dimensional memory devices having through stair contacts and methods for forming the same

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

• a memory stack comprising a plurality of interleaved conductive layers and dielectric layers, wherein edges of the interleaved conductive layers and dielectric layers define a staircase structure on a side of the memory stack;
• a word line contact in contact with one of the conductive layers of the memory stack at the staircase structure;
• and
• a through stair contact (TSC) extending vertically through the staircase structure of the memory stack, wherein a cross-section of the word line contact and a cross-section of the TSC have a same shape.

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

• a memory stack comprising a plurality of interleaved conductive layers and dielectric layers, wherein edges of the interleaved conductive layers and dielectric layers define a staircase structure in an outer region of the memory stack;
• a channel structure extending vertically through an inner region of the memory stack;
• and
• a through stair contact (TSC) extending vertically through the staircase structure inside the outer region of the memory stack, wherein the TSC comprises a metal layer.