Floating-gate / charge-trap transistor cell

Every solid-state drive, every smartphone, every memory card sold in India in 2026 relies on a memory cell that no Indian facility can make. The import dependence for the transistor cell at the heart of NAND flash is complete — 100 per cent.

The cell in question is deceptively small. In a floating-gate transistor, electrons are stored in a layer of polysilicon; in the charge-trap variant, they are stored in a film of silicon nitride. That nitride approach — realised in structures called SONOS and TANOS — packs cells closer together with less interference between neighbours, and is more robust against a single defect in the ultra-thin tunnel oxide. Samsung has claimed two-to-ten times the reliability over sub-20nm floating-gate cells. The economic verdict is already in: by the end of 2019, all charge-trap NAND bits ever shipped surpassed all floating-gate bits ever shipped over history.

The technology arrived commercially in 2002, when AMD and Fujitsu shipped charge-trap NOR flash under the MirrorBit name. From the late 2000s, Toshiba and Samsung made charge-trap cells the core of 3D V-NAND. Micron moved its 176-layer 3D NAND from floating-gate to charge-trap. Only six firms across South Korea, Japan, Taiwan, the United States and China command this at scale.

India's presence in this chain is real but confined to the finishing end. Sahasra Semiconductors runs an ATMP facility — assembly, test, marking and packaging — in Bhiwadi, Rajasthan, which began trials and sample production in March 2023. That is post-fabrication work. The cell itself is designed and fabricated elsewhere.

The gap persists because the cell sits atop a stack of foundational capabilities that India does not yet possess. Commercially viable cell design needs high-volume fabs at advanced nodes, and India's foundry capability is only emerging — the Tata-PSMC fab planned for Dholera, Gujarat, expected in 2027, targets display drivers, not memory. Beneath the fab lie the harder dependencies: photolithography, precise deposition of ultra-thin oxides and nitride by ALD and CVD, high-k dielectric materials, ion implantation. On the current assessment, India has none of these at production grade. Design and simulation tools (TCAD, EDA) and memory controller design are the relative bright spots.

What it would take is legible from the dependency chain. A commercial memory cell is not a single invention but the endpoint of lithography, deposition, dielectrics and implantation working in concert inside an advanced fab. The INR 76,000 crore Semicon India Programme funds the entry ticket — the fab — but the process capabilities below it must climb in step.