What is NAND flash memory?

How NAND flash works

NAND flash is a memory chip that keeps data without power. That sets it apart from DRAM, which stores data only temporarily, SK hynix's US stock offering prospectus explains. NAND is used in phones, memory cards and solid-state drives (SSDs). The prospectus says SSDs have replaced hard disk drives as the main storage in laptops and servers.

Each memory cell stores data as electrons held in a charge storage film, Kioxia explains. Whether electrons are there decides if the cell reads as a 0 or a 1. In NAND flash, the cells are connected in series, which lets them be packed closely. Kioxia says it invented NAND flash in 1987.

Chips are also classed by how many bits each cell stores. The classes run from single-level cells to quad-level cells and beyond, the prospectus says.

What 3D NAND and layer counts mean

In 3D NAND, memory cells are stacked vertically in layers. Kioxia says it announced the first 3D flash memory technology in 2007. Its development history says its own mass production switched from flat, 2D chips to 3D in the mid-2010s. Kioxia announced a 332-layer chip in 2025. SK hynix says it is moving its production from 176 layers to 238 and 321 layers.

Layer counts also matter for export controls. In October 2022, US rules added license requirements for items bound for China fabs making NAND with 128 layers or more, BIS said. Solidigm, SK hynix's US unit, uses 192 layers in the NAND it makes at a plant in Dalian, China, Blocks & Files reported. It said US export restrictions obstruct any upgrade of that plant to the latest technology.

Why NAND prices are rising

AI data centers store data on enterprise SSDs built with NAND. On September 30, 2026, TrendForce projected that NAND flash contract prices would rise 15% to 20% in the fourth quarter from the third. The market research firm said cloud providers' growing AI inference infrastructure would lift enterprise SSD bit demand by more than 80% in 2026.