Optical interferometric sensors represent the most advanced measurement tools in terms of precision and sensitivity for position detection. Micro-mechanical and micro-optical active and passive devices can be realized with present technologies on integrable substrates such as silicon wafers. We are working on the fabrication and characterization of micromirrors realized with micromachining technique. Our goal is to realize structures with a mechanical resonance frequency in ranges 1 kHz–100 kHz and 1 MHz–100 MHz. In these ranges we can think of different applications above all in the detection of gravitational waves and in quantum computation.