4DS - Anything but Charting, page-24561

I'm not sure 3D stacking is an immediate necessity. After all, 4DS is now chasing the DRAM augmentation market rather than NAND. Also, the 3D stacking of NAND was necessitated due to limitations in scaling cells beyond the 15-20nm range. To stack, the cells became larger.

If 4DS produces cells below 7nm, then they may produce bit densities well beyond the requirements of storage class memory. It will be far more cost-effective to exhaust the 2D development of the technology before looking into stacking.

Whether stacking is possible? Well, the answer may well lay in the birth of the 4DS acronym - 4 Dimensional Storage.