US Patent 9721668 3D non-volatile memory array with sub-block erase architecture

A memory device has a divided reference line structure which supports sub-block erase in NAND memory including a plurality of blocks. Each block in the plurality of blocks is coupled to a set of Y reference lines, where Y is two or more. Each block in the plurality of blocks includes a single reference select line (RSL), which is operable to connect each sub-block in the block to a corresponding reference line in the set of Y reference lines. A control circuit can be included on the device which is configured for an erase operation to erase a selected sub-block in a selected block.