A new wake-up receiver (WuRx) designed in 0.13 μm CMOS process is hybrid-integrated with a micro-electromechanical system (MEMS) RF resonator. While only consuming 166 nW of power (18.8 nW for the comparator and 147 nW for periphery), the WuRx is capable of detecting RF signals as weak as -60 dBm. In order to achieve this sensitivity, a passive voltage-boosting network comprised of a high quality factor (high-Q) piezoelectric MEMS resonator is utilized, in place of an inductor, to amplify the received voltages applied to a CMOS rectifier. The output of the rectifier is then applied to a low-power comparator used to set a logical bit that indicates when an RF signal has been detected. The trade-offs in designing the voltage boosting network are explained and an equation for the optimum number of rectifier stages is derived.