FinFET
The transistor type that has dominated chip manufacturing since ~2011, where the channel stands up as a "fin" and the gate surrounds it on three sides. It solved the leakage problems that killed the old flat (planar) transistor at small nodes.
Background: at ~22 nm planar transistors became too leaky — the gate (on just one side) couldn't turn the current off properly. FinFET raises the channel vertically and hugs it on three sides → much better control, lower leakage, higher performance. Intel introduced it commercially in 2011 ("Tri-Gate") at 22 nm; everyone followed. It reigned down to ~3 nm. At 2 nm, three sides no longer provide enough control → gate-all-around (four sides) takes over. FinFET was the decisive step that kept Moore's law alive for a decade. Related to gate-all-around and process node.