Silicon nitride, silicon dioxide, and silicon oxynitride films have been deposited using RPCVD, in which the substrate temperature is low (∼250℃)and the electronic damage is negligible because plasma region is separated from deposition chamber. Nearly Stoichiometric $SiO_2$ and $Si_3N_4$ have been deposited and incorporated bonded hydrogen concentrations were very low. And in silicon nitride and silicon oxynitride, the refractive indices can be vary in wide range by varying the composition ratio of the reactant gases. As an application to MMIC, MIM capacitors, which are bottleneck of yield in MMIC are fabricated using these silicon nitrides and obtained very good characteristics as dielectric materials. And as an application to OEIC, dielectric optical waveguides are fabricated using these films as guiding layers and OPS as an buffer layer. Also, bend-type waveguide, which is adequate for efficient small size OEIC implementation, is proposed and fabricated.