Method of suppressing epitaxial growth in support openings and three-dimensional memory device containing non-epitaxial support pillars in the support openings

A monolithic three-dimensional memory device comprising:

• at least one alternating stack of insulating layers and electrically conductive layers located over a semiconductor substrate;
• memory openings extending through the at least one alternating stack, wherein each of the memory openings is filled with an epitaxial channel portion contacting the semiconductor substrate and a memory stack structure;
• and
• support openings extending through the at least one alternating stack, wherein each of the support openings is filled with a support pillar structure,
• wherein:
• each of the memory stack structures and the support pillar structures comprise an instance of a layer stack including charge storage material portions, a tunneling dielectric layer, and at least one vertical semiconductor layer;
• each instance of the layer stack in the memory stack structures is vertically spaced from the semiconductor substrate by a respective epitaxial channel portion;
• and
• each instance of the layer stack in the support pillar structures is in physical contact with an impurity-doped semiconductor material portion within the semiconductor substrate.