FinFET

FinFET architecture raises a thin vertical silicon fin above the substrate and wraps gate material around three of its four sides (the top and two sidewalls, but not the bottom, which remains attached to the substrate), giving substantially better electrostatic channel control than the planar transistors it succeeded. FinFET's three-sided, rather than fully four-sided, gate coverage is precisely the structural limitation that eventually motivated the industry's further transition to gate-all-around architecture, which wraps gate material completely around the channel on all sides rather than leaving one side unavoidably attached to the substrate.