A memory device includes an alternating stack of insulating layers and electrically conductive layers located over a substrate, a memory opening vertically extending through the alternating stack, and a memory opening fill structure located in the memory opening and including a vertical semiconductor channel and a memory material layer. A vertical stack of insulating material portions can be provided at levels of the insulating layers to provide a laterally-undulating profile to the memory material layer. Alternatively, a combination of inner insulating spacers and outer insulating spacers can be employed to provide a laterally-undulating profile to the memory material layer.