The need for miniaturized frequency-selective components in electronic systems is clear. The questions are whether and how micro-electro-mechanical systems (MEMS) can satisfy the need. This dissertation aims to address these questions from a scientific perspective. Silicon is the focus of this work, as it can benefit from scaling of the semiconductor industry. Silicon also offers many technical advantages. The characteristics of silicon resonators from 32 kHz to 1 GHz are described. The temperature stability and phase noise of a 6-MHz temperature-compensated oscillator and a 100-MHz temperature-controlled oscillator are reported. Silicon resonator design and characterization, with a focus on quality factor, linearity, and the electrical equivalent circuit, are included. Electrical tuning, electromechanical coupling, finite element modeling, and unexpected findings of these resonators are also described. A manufacturability technique employing batch process compensation is demonstrated. Results indicate that silicon is an excellent material for micromechanical resonators. The aim of this research is to explore the fundamental limitations, provide a foundation for future work, and also paint a clearer picture on how micromechanical resonators can complement alternative technologies.

Frequency reference oscillator is a critical component of modern radio transceivers. Currently, most reference oscillators are based on low-frequency quartz crystals that are inherently bulky and incompatible with standard micro-fabrication processes. Moreover, their frequency limitation (<200MHz) requires large up-conversion ratio in multigigahertz frequency synthesizers, which in turn, degrades the phase-noise. Recent advances in MEMS technology have made realization of high-frequency on-chip low phase-noise MEMS oscillators possible. Although significant research has been directed toward replacing quartz crystal oscillators with integrated micromechanical oscillators, their phase-noise performance is not well modeled. In addition, little attention has been paid to developing electronic frequency tuning techniques to compensate for temperature/process variation and improve the absolute frequency accuracy. The objective of this dissertation was to realize high-frequency temperature-compensated high-frequency (>100MHz) micromechanical oscillators and study their phase-noise performance. To this end, low-power low-noise CMOS transimpedance amplifiers (TIA) that employ novel gain and bandwidth enhancement techniques are interfaced with high frequency (>100MHz) micromechanical resonators. The oscillation frequency is varied by a tuning network that uses frequency tuning enhancement techniques to increase the tuning range with minimal effect on the phase-noise performance. Taking advantage of extended frequency tuning range, and on-chip temperature-compensation circuitry is embedded with the sustaining circuitry to electronically temperature-compensate the oscillator. Finally, detailed study of the phase-noise in micromechanical oscillators is performed and analytical phase-noise models are derived.