A three-dimensional memory device includes an alternating stack of insulating layers and electrically conductive layers located over a substrate, memory openings vertically extending through a first region of the alternating stack, memory opening fill structures located in the memory openings, and support pillar structures vertically extending through a second region of the alternating stack. Each of the support pillar structures includes a central columnar structure and a set of fins laterally protruding from the central columnar structure at levels of a subset of the electrically conductive layers.