Three-dimensional memory device and formation method thereof

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

• a stack structure comprising a plurality of alternating conductive layers and dielectric layers, the stack structure having a first region and a second region;
• gate line slit structures extending through the stack structure and dividing the stack structure into a plurality of memory blocks;
• and
• a contact located in the second region and comprising a first portion extending from a surface of the stack structure to a target conductive layer of the conductive layer and a second portion covering part of the surface of the stack structure,
• wherein a material of the first portion and the second portion of the contact is same as a material of the conductive layers.

A memory system, comprising:

• a memory device configured to store data, the memory device comprising:
• a stack structure comprising a plurality of alternate conductive layers and dielectric layers, and having a first region and a second region;
• gate line slit structures extending through the stack structure and dividing the stack structure into a plurality of memory blocks;
• and
• a contact in the second region and comprising a first portion extending from a surface of
• the stack structure to a target conductive layer and a second portion covering a part of the surface of the stack structure, wherein the first portion and the second portion of the contact comprise a same material as the conductive layers;
• and
• a memory controller coupled to the memory device and configured to control the memory device.