Abstract: A three-dimensional memory device includes an alternating stack of insulating layers and electrically conductive layers, memory opening fill structures located within a respective memory opening vertically extending through the alternating stack in a memory array region, and support pillar structures vertically extending through the alternating stack. Each of the memory opening fill structures includes a respective vertical semiconductor channel and a respective memory film that contacts each layer within the alternating stack. Each of the support pillar structures includes a respective dummy vertical semiconductor channel, a respective dummy memory film, and at least one respective dielectric spacer material portion laterally surrounding the respective dummy memory film and interposed between the electrically conductive layers and the respective dummy memory film.