trigate

Trigate refers to a three-dimensional transistor design in which the gate electrode surrounds the channel on three faces. The most common implementation is a fin field-effect transistor (FinFET), where a thin vertical silicon fin forms the channel and the gate wraps around the top and two sidewalls of the fin. The term “tri-gate” is often used to describe these FinFET-based devices, especially in early industry literature.

Structure and operation: A narrow silicon fin protrudes from the substrate to form the transistor channel. Source and drain are located at opposite ends of the fin, while the gate encloses the fin on three sides—top and two lateral faces—separated from the channel by a gate dielectric. This three-sided gate provides stronger electrostatic control over the channel than a planar gate, helping suppress short-channel effects and allowing continued scaling.

Advantages and impact: Tri-gate/FinFET architectures offer reduced leakage in the off state and steeper subthreshold slopes, enabling higher drive currents for the same footprint. The enhanced gate control improves device performance and scaling potential compared with traditional planar MOSFETs, making FinFET-based transistors a common choice for sub-20 nanometer technological nodes. Variants and evolutions have moved toward gate-all-around (GAA) structures for even more channel wrap.

History and usage: The concept of multi-gate transistors emerged in academia and industry as a solution to scaling challenges in the 1990s and 2000s. FinFET/tri-gate implementations were commercialized in the early 2010s, notably by Intel for its 22 nm node and by other foundries thereafter. Today, FinFET remains a standard term for three-gate transistors, while further scaling has led to GAA architectures that extend the gate wrap-around even further.