Due to the strong influence of interface, layer thickness and film surface quality on the efficiency of multi-layer dielectric thin film based devices, a careful analysis of these films by neutron is mandatory. Our goal is to clarify the effect of the synthesis of silicon nitride and oxynitride thin film on the layer properties and configurations of constituent atoms. This is to understand the charge and discharge behavior of these dielectric thin films used in our capacitive RF-MEMS switches under the actuation of DC electric field.Neutron reflection is in the analysis of thin layers for structural and morphological characterization and will be dedicated to the problems in our thin films with different scattering lengths and atomic density.