X-DIRECTION DIVIDED SUB-BLOCK MODE IN NAND

A memory system is described having an x-direction (bit line direction) divided sub-block mode. Each block is divided in a y-direction and in the x-direction into a number of groups of contiguous NAND strings that are referred to as XY sub-blocks. The memory system performs a memory operation in parallel in multiple XY sub-blocks in a block while inhibiting the memory operation in the other XY sub-blocks in the block. Each XY sub-block for which the memory operation is performed has its NAND strings connected to a different set of contiguous bit lines. In an aspect the memory operation is a program operation with selected memory cells in each of the multiple XY sub-blocks programmed in parallel while inhibiting programming of all memory cells in all other XY sub-blocks in the block. In one aspect, the memory operation is an erase operation.