Over the last decade, silicon pressure sensors have undergone a significant growth. In most cases, these MEMS (Microelectromechanical System) devices are manufactured from rectangular or circular diaphragms whose thickness is constant and in the order of some microns. The development of high-performance diaphragm structure is of critical importance in the successful realization of the devices. In particular, diaphragms capable of linear deflection are needed in many pressure sensors. In order to increase the sensitivity, the diaphragm thickness should be thin to maximize the load-deflection responses. On the other hand, thin diaphragm under high pressure may result in large deflection and nonlinear effects that are not desirable. It is therefore important to characterize the relationship between diaphragm thickness, deflection, and sensitivity, both analytically and experimentally in order to establish the design guidelines for micro pressure sensors.