金属半导体场效应管（英语：metal semiconductor field effect transistor, MESFET），简称金半场效应管，是一种在结构上与结型场效应管类似，不过它与后者的区别是这种场效应管并没有使用PN结作为其栅极，而是采用金属、半导体接触结，构成肖特基势垒的方式形成栅极。金属半导体场效应管通常由化合物半导体构成，例如砷化镓、磷化铟、碳化硅等，它的速度比由硅制造的结型场效应管或MOSFET更快，但是造价相对更高。金属半导体场效应管的工作频率最高可以达到45 GHz左右，在微波频段的通信、雷达等设备中有着广泛应用。第一个金属半导体场效应管在1966年被发明，其良好的极高频性能在随后的一年即展现出来。在数字电路设计领域，由于数字集成电路的集成度不断提高，因此使用金属半导体场效应管并不如CMOS。

MESFET stands for metal–semiconductor field-effect transistor. It is quite similar to a JFET in construction and terminology. The difference is that instead of using a p-n junction for a gate, a Schottky (metal-semiconductor) junction is used. MESFETs are usually constructed in compound semiconductor technologies lacking high quality surface passivation such as GaAs, InP, or SiC, and are faster but more expensive than silicon-based JFETs or MOSFETs. Production MESFETs are operated up to approximately 45 GHz, and are commonly used for microwave frequency communications and radar. The first MESFETs were developed in 1966, and a year later their extremely high frequency RF microwave performance was demonstrated.