Three-dimensional memory devices and methods for forming the same

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

• a semiconductor layer;
• a stack structure comprising interleaved conductive layers and dielectric layers, wherein edges of the interleaved conductive layers and dielectric layers define a staircase structure, and each one of the conductive layers has a thickened portion in the staircase structure, the thickened portion extending along a first direction;
• and
• a channel structure extending through the stack structure and in contact with the semiconductor layer,
• wherein at least the thickened portion of a first conductive layer of the conductive layers is continuous along the first direction;
• and
• at least the thickened portion of a second conductive layer of the conductive layers is discontinuous along the first direction, the first conductive layer being closer to the semiconductor layer than the second conductive layer.

A method for forming a three-dimensional (3D) memory device, comprising:

• forming a stack structure comprising interleaved first material layers and second material layers;
• forming a staircase structure of the stack structure;
• forming third material layers each disposed on a respective one of the first material layers in the staircase structure and extending along a first direction;
• and
• forming a slit opening extending through the stack structure and along a second direction perpendicular to the first direction, such that the slit opening cuts off at least one, but not all, of the third material layers.