A three-dimensional memory device includes layer stacks located over a substrate and laterally spaced apart from each other by backside trenches. Each of the layer stacks includes a respective alternating stack of insulating layers and electrically conductive layers. Memory openings vertically extend through a respective one of the alternating stacks and are filled with a respective memory opening fill structure. Each of the memory opening fill structures includes a respective vertical semiconductor channel and a respective vertical stack of memory elements. Each backside trench fill structure includes a respective row of backside trench bridge structures that are more distal from the substrate than a most distal one of the electrically conductive layers is from the substrate. The backside trench bridge structures can provide structural support during a replacement process that forms the electrically conductive layers.