GaAs-based micromachining is a very attractive technique for integrating mechanical structures and active optical devices such as laser diodes and photodiodes. For the monolithic integration of micromechanical parts onto laser diode wafers, the compatibility to a laser diode fabrication process is essential. Our micromachining technique features three major processes of epitaxial growth (MOVPE) for both structural and sacrificial layers, reactive dry-etching by chlorine for high-aspect, three-dimensional structures, and selective wet-etching by peroxide/ammonium hydroxide solution to release the moving parts. These processes are compatible with laser fabrication, so a cantilever beam structure can be fabricated at the same time as a laser diode structure. Furthermore, a single-crystal epitaxial layer has little residual stress, so precise microstructures can be obtained without significant deformation. We fabricated a microbeam resonator sensor composed of two laser diodes, a photodiode, and a micro- cantilever beam with an area of 400 micrometers X 700 micrometers . the cantilever beam is excited by an intensity modulated laser beam from an integrated excitation laser diode, and the vibration signal is detected by a couple cavity laser diode and photodiode.