Three-dimensional memory device containing through-array contact via structures between dielectric barrier walls and methods of making the same

A method for forming a three-dimensional memory device, comprising:

• forming an alternating stack of insulating layers and sacrificial material layers over a semiconductor substrate, wherein the sacrificial material layers comprise a dielectric material;
• forming memory stack structures through the alternating stack;
• patterning the alternating stack by performing an anisotropic etch process using a patterned mask layer, wherein the alternating stack is divided into a plurality of alternating stacks of respective insulating layers and respective sacrificial material layers by backside trenches, and wherein a pair of unconnected barrier trenches is formed through each of the plurality of alternating stacks;
• forming backside recesses by isotropically etching portions of the sacrificial material layers of the plurality of alternating stacks selective to the insulating layers of the plurality of alternating stacks by introducing an isotropic etchant into the backside trenches while the barrier trenches are covered by a respective dielectric liner that blocks access of the isotropic etchant to adjacent portions of the sacrificial material layers, wherein remaining portions of the sacrificial material layers between each neighboring pair of barrier trenches constitute dielectric spacer plates, and a vertically alternating sequence of the insulating plates and the dielectric spacer plates is provided between the pair of barrier trenches;
• forming electrically conductive layers in the backside recesses;
• and
• forming at least one conductive via structure through the vertically alternating sequence.