Methods for forming three-dimensional memory devices with channel structures having plum blossom shape

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

• forming a channel hole extending vertically above a substrate and having a plum blossom shape in a plan view;
• sequentially forming a blocking layer, a charge trapping layer, and a tunneling layer each following the plum blossom shape along sidewalls of the channel hole;
• forming a semiconductor channel layer over the tunneling layer, such that an apex thickness of the semiconductor channel layer at each apex of the plum blossom shape is greater than an edge thickness of the semiconductor channel layer at edges of the plum blossom shape;
• and
• removing parts of the semiconductor channel layer at the edges of the plum blossom shape to separate the semiconductor channel layer into a plurality of semiconductor channels each at a respective apex of the plum blossom shape.

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

• forming a channel hole extending vertically above a substrate and having a plum blossom shape in a plan view;
• forming a continuous blocking layer, a continuous charge trapping layer, and a continuous tunneling layer each following the plum blossom shape from outside to inside in this order along sidewalls of the channel hole;
• and
• forming a plurality of separate semiconductor channels each disposed over part of the continuous tunneling layer at a respective apex of the plum blossom shape.