We present a design approach that enables monolithic integration of high-quality-factor (Q) radio-frequency (RF) microelectromechanical systems (MEMS) resonators with CMOS electronics. Commercially available CMOS processes that feature two polysilicon layers and field oxide isolation can be used to implement this approach. By using a nonplanar resonator geometry in conjunction with mechanical stress in polycrystalline silicon (poly) gate layers, we create rigid and robust mechanical structures with efficient electromechanical transduction. We demonstrate polysilicon domes with capacitive pickup and arch-bridge resonators with piezoresistive readout. The small footprint of our MEMS structures enables on-chip integration of large arrays of resonators for RF signal processing or sensing applications. Their large surface-to-volume ratio in combination with high rigidity (that alleviates stiction associated with wet chemistry processing) can make these resonators particularly useful for sensors that require surface functionalization. © 2010 IEEE.