| CPC H10B 41/27 (2023.02) [G11C 16/0483 (2013.01); H10B 41/10 (2023.02); H10B 41/35 (2023.02); H10B 43/10 (2023.02); H10B 43/27 (2023.02); H10B 43/35 (2023.02)] | 17 Claims |

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1. A memory device, comprising:
an alternating stack of insulating layers and electrically conductive layers;
an insulating cap layer that overlies the alternating stack;
a memory opening vertically extending through the alternating stack and the insulating cap layer; and
a memory opening fill structure located in the memory opening and comprising a vertical semiconductor channel, a memory film, and a drain region comprising a doped semiconductor material contacting an end portion of the vertical semiconductor channel and having a top surface located within a horizontal plane including a top surface of the insulating cap layer,
wherein the memory film comprises a memory material layer consisting essentially of silicon nitride and having a straight inner cylindrical sidewall that continuously vertically extends through a plurality of electrically conductive layers within the alternating stack and through the insulating cap layer without lateral undulation and a laterally-undulating outer sidewall having outward lateral protrusions at levels of the plurality of electrically conductive layers, wherein a topmost outward lateral protrusion of the laterally-undulating outer sidewall of the memory material layer is located at a level of a topmost electrically conductive layer of the electrically conductive layers, and laterally protrudes outward relative to a topmost vertically-extending segment of the laterally-undulating outer sidewall located at a level of the insulating cap layer, wherein an entirety of the straight inner cylindrical sidewall consists essentially of the silicon nitride, and an entirety of the laterally-undulating outer sidewall consists essentially of the silicon nitride.
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