Three-dimensional memory device with horizontal silicon channels and method of making the same

A three-dimensional memory device, comprising:

• multi-fingered silicon layers which are vertically spaced from one another and which are located over a substrate, wherein each of the multi-fingered silicon layers includes a respective silicon plate portion and a respective set of silicon wires extending along a first horizontal direction and laterally spaced apart along a second horizontal direction;
• tubular memory films which surround respective portions of each of the silicon wires;
• gate electrodes comprising vertically-extending gate electrode fingers, wherein each of the vertically-extending gate electrode fingers extends vertically between a respective laterally-neighboring pair of silicon wires, wherein the gate electrodes are laterally spaced apart along the first horizontal direction, and wherein each of the silicon wires comprises a respective channel portion that is undoped or has a doping of a first conductivity type and extending under each of the gate electrodes;
• first active regions located at an end portion of each of the silicon wires and having a doping of a second conductivity type that is an opposite of the first conductivity type;
• and
• second active regions located in the silicon plate portions of the multi-fingered silicon layers and having a doping of the second conductivity type;
• wherein:
• each of the silicon wires includes a laterally alternating sequence of rounded sections and rectangular sections;
• each of the rounded sections has a vertical cross-sectional shape of a circle, an ellipse, or a rounded rectangle;
• and
• each of the rectangular sections has a vertical cross-sectional shape of a rectangle.