Silicon micromechanical resonators have recently shown tremendous potential for replacing quartz crystal resonators in various radio frequency applications such as mass sensing and precision timing. Their small form factor and ability to integrate into conventional integrated circuit technology are the main reasons MEMS resonators are attractive devices in various applications. In this research different bulk mode resonators are investigated for mass sensing and precise timing application. More focus has been put on integration of the MEMS resonator with CMOS circuit that makes proposed devices more reliable and miniaturized. The fabricated devices in our lab are electrostatically stimulated and capacitive variation is used for formation of the output signal.