MEMS oscillators, which include a silicon-type, in particular piezoresistive resonators, can be used to provide a fixed, stable output frequency. Silicon has a natural temperature dependence of Young's modulus, therefore, as ambient temperature changes and/or the piezoresistive resonator is powered, the resonator temperature changes, and the resonance frequency of the resonator drifts. In order to account for the temperature drift of the piezoresistive resonator, the piezoresistive resonator itself is used as a temperature sensor. The relative resistance change of the piezoresistive resonator depends only on the relative temperature change and material property of the resonator. Therefore, an accurate temperature can be sensed directly on the piezoresistive resonator. The temperature drift information is provided to a frequency adjuster, which corrects the output frequency of the circuit.