A vertical resistive unit is provided. The vertical resistive unit includes first and second resistive random access memory (ReRAM) cells. The first ReRAM cell includes first vertically aligned horizontal electrode layers and first vertical electrodes operably extending through the first vertically aligned horizontal electrode layers. The second ReRAM cell includes second vertically aligned horizontal electrode layers and second vertical electrodes operably extending through the second vertically aligned horizontal electrode layers. The first and second ReRAM cells are disposed to define an air gap between the first and second ReRAM cells.