Memory array including memory cell strings and method for forming memory array including memory cell strings

The invention relates to a memory array including strings of memory cells and a method for forming a memory array including strings of memory cells. A memory array includes laterally spaced memory blocks, the memory blocks individually including a vertical stack including alternating insulating layers and conductive layers directly over a conductor layer. A string of memory cells includes a string of channel material extending through the insulating layer and the conductive layer. The channel material string is electrically coupled directly to a conductor material of the conductor layer. Through array via (TAV) regions include TAVs that individually extend through a lowermost one of the conductive layers. An insulating ring is in the lowermost conductive layer in the TAV region. Individual ones of the insulating rings surround individual ones of the TAVs. The insulating ring extends through the lowermost conductive layer and into the conductor layer. An outer ring is in the lowermost conductive layer, the out