The CrN/Si3N4 nano-structured multilayer films on Si (1 0 0) wafers have been fabricated by radio-frequency reactive magnetron sputtering. The microstructures, surface topography and properties of the films have been studied by X-ray diffraction, Auger electron spectroscopy, X-ray reflectivity, atomic force microscopy and nano-indenter. The CrN and Si3N4 single layer films are polycrystalline face-centered-cubic and amorphous structures, respectively. The CrN and Si3N4 layers in the multilayers are nearly stoichiometric. The interfaces between the CrN and Si3N4 layers are very sharp because they do not form an interfacial phase. The surface topography shows that the multilayers of CrN/Si3N4 at a small modulation period are much smoother than their constituent CrN and Si3N4 monolithic films. This results from the interruption of the columnar grain growth by alternating deposition of crystal CrN and amorphous Si3N4. The hardness values of the multilayers at different modulation periods are between those of the constituent CrN and Si3N4 films. The superhardness effect was not observed in this system. The relationships between microstructures and mechanical properties are discussed.