We present 4-terminal (4-T) silicon (Si) nanoelectron-mechanical (NEM) relays fabricated on silicon-on-insulator (SOI) wafers. We demonstrate true 4-T switching behavior with isolated control and signal paths. A pull-in voltage (Vpi ) as low as 11.6 V is achieved with the miniaturized design. 4-T NEM relays are a very promising candidate for building ultra-low-power logic circuits, since they enable novel circuit architectures to realize logic functions with far fewer devices than CMOS implementations, while also allowing the dynamic power consumption to be reduced by body-biasing.