Three-dimensional memory device with a conductive drain-select-level spacer and methods for forming the same

A three-dimensional memory device, comprising:

• an alternating stack of insulating layers and electrically conductive layers, wherein the electrically conductive layers comprise word-line-level electrically conductive layers and drain-select-level electrically conductive layers located above the word-line-level electrically conductive layers;
• a first backside trench fill structure extending along a first horizontal direction and comprising a first dielectric surface that contacts first sidewalls of each layer within the alternating stack;
• a second backside trench fill structure extending along the first horizontal direction, separated from the first backside trench fill structure along a second horizontal direction perpendicular to the first horizontal direction, and comprising a second dielectric surface that contacts second sidewalls of each layer within the alternating stack;
• a contact-level dielectric layer overlying the alternating stack;
• drain-select-level isolation structures extending through the contact-level dielectric layer and the drain-select-level electrically conductive layers but not through the word-line-level electrically conductive layers of the alternating stack, wherein the drain-select-level isolation structures extend in the first horizontal direction and are spaced apart along the second horizontal direction;
• memory opening fill structures vertically extending through the alternating stack in a memory array region in which each layer within the alternating stack is present, wherein each of the memory opening fill structures comprises a vertical semiconductor channel and a memory film, wherein an entirety of the memory opening fill structures underlies a bottom surface of the contact-level dielectric layer;
• an electrically conductive spacer extending vertically and electrically connecting a first drain-select-level electrically conductive layer of the drain-select-level electrically conductive layers to a second drain-select-level electrically conductive layer of the drain-select-level electrically conductive layers, wherein the electrically conductive spacer extends along the second horizontal direction and contacts ends of the first and the second drain-select-level electrically conductive layers along the second horizontal direction;
• and
• an additional electrically conductive spacer extending vertically and electrically connecting a third drain-select-level electrically conductive layer of the drain-select-level electrically conductive layers to a fourth drain-select-level electrically conductive layer of the drain-select-level electrically conductive layers.