Microelectromechanical devices such as accelerometers, gyroscopes, pressure sensors, and radiofrequency (RF) switches are widely used in aerospace applications. Reduction of stiffening and curling initiated during fabrication of these devices is one of the challenging issues in MEMS design. Reducing response time is also favorable in some applications such as RF MEMS switches. This paper aims at reducing stiffening, curling, and increasing the natural frequency for three well-known designs of micro-plates with fixed-fixed supports. To achieve these objectives, a parametric size optimization is carried out. For comparison purposes, same volume is set as a constraint for all three designs. Compared to conventional rectangular micro-plate, a reduction of 34% in stiffening in design 2, and 44% in curling in design 3. Design 1 showed the maximum fundamental natural frequency. Thus, it is predicted to have the lowest switching time. Moreover, design 2 showed the maximum critical buckling temperature, extending the operation range of the device. The effect of changing micro-plate material is also studied in this paper.