This thesis work, carried out at Nanofabrication facility of the Molecular Foundry, a division of the Lawrence Berkeley National Laboratory (LBNL), focuses in a Multidisciplinary project involving the optimization of several nano-fabrication processes of optical, electronical and mechanical parts of Multifunctional Optoelectronic Neural Probes aimed at high density parallel read-out and control of the central nervous system for in vivo experiments in rats. The probe consists on a micro tip able to sense and stimulate the brain tissue exploiting a set of electrodes for the read out and an optical system to selectively excite neurons with high temporal and spatial resolution.