In recent years, the technology of polycrystalline silicon was much developed and has found numerous applications in microelectronics in general and in micromachined sensors and microactuators, in particular. In these new electronic devices, various types of substrates are very often mixed. For some applications as bio-chips, actuators, it may be useful to coat selectively designated areas of mixed polycrystalline/single-crystal silicon devices. The present work was undertaken within this point of view. Selective organic coating of designated areas of mixed poly and monocrystalline devices was obtained with a mask-free technique by applying electroless or electro-induced processes.