Gate-all-around (GAA)
A new transistor structure succeeding FinFET, where the gate surrounds the channel on all four sides instead of three. It gives better control over the current and less leakage, necessary for nodes at 2 nm and below. Intel calls its variant RibbonFET.
Why: the smaller transistors get, the harder to fully turn them off → leakage current and energy waste. FinFET (three sides) lasted down to ~3 nm; GAA wraps the gate completely around stacked "nanosheets" → maximum electrostatic control, lower leakage, higher performance per watt. Samsung was first in production (3 nm GAA), TSMC introduces it at N2, Intel with RibbonFET at 20A/18A. GAA is often paired with backside power delivery for an additional gain. The big transistor step for the 2 nm era. Related to FinFET and backside power.