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

1. 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;

wherein:

each of the drain-select-level dielectric isolation structures has a uniform width along the second horizontal direction and contacts bottom surfaces of a respective row of the drain regions that is arranged along the first horizontal direction; and

each of the memory opening fill structures comprises a dielectric core contacting inner sidewalls of the two vertical semiconductor channels and contacting a pair of lengthwise sidewalls and a bottom surface of a respective one of the drain-select-level dielectric isolation structures.

2. The three-dimensional memory device of claim 1 , wherein each of the memory opening fill structures comprises a drain region contacting top surfaces of the two vertical semiconductor channels and located over a respective one of the drain-select-level dielectric isolation structures.

3. The three-dimensional memory device of claim 2 , further comprising a plurality of drain side select transistors, wherein each of the drain side select transistors comprises a drain side select gate electrode and an upper portion of the vertical semiconductor channel, and wherein the two vertical semiconductor channels in the same memory opening fill structure are controlled by different drain side select transistors of the plurality of drain side select transistors.

4. The three-dimensional memory device of claim 1 , wherein the two vertical semiconductor channels within each of the memory opening fill structures have a respective crescent-shaped horizontal cross-sectional profile.

5. The three-dimensional memory device of claim 1 , further comprising:

a source layer electrically connected to bottom ends of the vertical semiconductor channels; and

a logic die bonded to the memory die.