Three-dimensional memory device with plural channels per memory opening and methods of making the same

A three-dimensional memory device comprising a memory die that includes:

• an alternating stack of insulating layers and electrically conductive layers;
• memory openings vertically extending through the alternating stack;
• memory opening fill structures located in the memory openings, wherein each of the memory opening fill structures comprises a memory film and two vertical semiconductor channels, and the memory openings and the memory opening fill structures are arranged in rows that laterally extend along a first horizontal direction and are laterally spaced from each other along a second horizontal direction;
• and
• drain-select-level dielectric isolation structures extending through each row of the memory opening fill structures at least at a level of a topmost one of the electrically conductive layers.

A method of forming a three-dimensional memory device, comprising:

• forming an alternating stack of insulating layers and sacrificial material layers over a substrate;
• forming memory openings through the alternating stack;
• forming a memory film in each of the memory openings;
• forming a semiconductor channel layer over the memory film;
• and
• performing a curvature-dependent lateral etch process that etches surfaces of the semiconductor channel layer having a lower curvature at a higher etch rate than surfaces of the semiconductor channel layer having a higher curvature, wherein remaining portions of the semiconductor channel layer comprise pairs of vertical semiconductor channels located within a respective one of the memory openings.