Micro-electro-mechanical systems (MEMS) are microscopic mechanical systems coupled with electric or electronic circuits. MEMS have been extensively used as micro-scale high-quality oscillators, communication resonators, microphones, amplifiers and other micro-oscillators. In this investigation, mathematical model of a micro-mechanical resonator is developed subject to a full nonlinear model. The governing equation is a nonlinear parametric and hence, the stability of the system depends on the value of its parameters. The output signal of MEMS is not reliable when it is operating in a saturated or in an instable region. From a design viewpoint, a stability chart is needed to indicate the relationship between the parameters to determine when the system is stable, periodic, or unstable. Nondimensional and linearized model of the MEMS is studied and a stability diagram is developed for the system.