This paper presents a dual-microelectromechanical system (MEMS) resonator-based temperature sensor. In this sensor, the readout circuit estimates the temperature by measuring the frequency ratio of the two clocks generated by separate resonators with different temperature coefficients. The circuit is realized in a 0.18-μm CMOS process and achieves a resolution of 20 μK over a bandwidth of 100 Hz while consuming 19 mW of power, leading to a resolution FOM of 0.04 pJK ² . It enables us to implement a MEMS-based programmable oscillator with an Allan deviation of <;1e ^-10 over 1 s averaging time, and a frequency stability of <;±0.1 parts per million in the temperature range from -45 °C to 105 °C. Such oscillators are key building blocks in telecom, datacom, and precision timekeeping applications.