FinFET

A FinFET (fin field-effect transistor) is a non-planar, three-dimensional transistor in which the conducting channel is raised into a thin vertical "fin" of silicon, and the gate is draped over two or three sides of that fin. Wrapping the gate around the channel gives it far better electrostatic control than a flat device, suppressing the leakage currents that plagued aggressive transistor shrinks in the 2000s. This is the switching element packed by the billion into every modern Bitcoin mining ASIC, where leakage directly translates into wasted watts and lower efficiency.

Why mining cares about fins

SHA-256 ASICs are judged almost entirely on joules per terahash. Because a FinFET's wrapped gate shuts the channel off more completely when idle, it leaks less static power and can run at a lower voltage for the same speed, both of which improve efficiency. Antminer and Whatsminer generations from roughly the S9 era onward ride successive FinFET nodes to push hashrate up while holding power in check.

From 22nm to the GAAFET handoff

Intel commercialized the first FinFETs (which it branded tri-gate) at the 22nm node in 2012, and the structure became the dominant logic transistor across 14nm, 10nm, and 7nm. Below about 3nm the fin can no longer be controlled well enough, so the industry transitions to gate-all-around successors. FinFETs replaced the older flat architecture that preceded them.

FinFETs evolved directly from the older planar transistor and are now giving way to the GAAFET; their relentless shrink is what kept Moore's Law alive through the 2010s.