3D NAND – Three dimensional NAND is a flash chip built so that it scales in width, length and height. Originally NAND scaled in just two dimensions – width and length – and was called planar NAND. The 3D NAND concept involves changing the orientation of planar NAND cells to enable layers of them to be stacked inside a die.

3D NAND concept diagram

The number of layers has increased over the generations of 3D NAND and could ultimately rise to 1,000.