Methods for forming three-dimensional memory devices with supporting structure for staircase region

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

• sequentially forming a first semiconductor layer, a first block layer, and a sacrificial layer on a substrate;
• replacing part of the first block layer and the sacrificial layer with a supporting structure;
• forming a dielectric stack above the supporting structure and a remainder of the sacrificial layer and having a staircase region, such that the supporting structure overlaps the staircase region of the dielectric stack;
• forming a channel structure extending vertically through the dielectric stack, the remainder of the sacrificial layer, and the first block layer, into the first semiconductor layer;
• forming an opening extending vertically through the dielectric stack to expose part of the remainder of the sacrificial layer;
• and
• replacing, through the opening, the remainder of the sacrificial layer with a second semiconductor layer coplanar with the supporting structure.

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

• forming a peripheral circuit on a first substrate;
• forming a first semiconductor layer on a second substrate;
• forming a supporting structure and a second semiconductor layer coplanar with the supporting structure on the first semiconductor layer;
• forming a memory stack above the supporting structure and the second semiconductor layer, the memory stack having a staircase region overlapping the supporting structure;
• forming a channel structure extending vertically through the memory stack and the second semiconductor layer into the first semiconductor layer;
• and
• bonding the first substrate and the second substrate in a face-to-face manner.