THREE-DIMENSIONAL MEMORY DEVICE CONTAINING MULTI-LEVEL SUPPORT BRIDGE STRUCTURES AND METHODS FOR FORMING THE SAME

A semiconductor structure includes alternating stacks of insulating layers and electrically conductive layers which are located over a substrate and are laterally spaced apart from each other by first backside trenches and second backside trenches that are interlaced along a horizontal direction, first backside trench fill structures located in the first backside trenches, and second backside trench fill structures located in the second backside trenches. Each of the first backside trench fill structures includes a respective set of first backside support bridge structures located at a first vertical spacing from the substrate, and each of the second backside trench fill structures includes a respective set of second backside support bridge structures located at a second vertical spacing from the substrate that is different from the first vertical spacing.