The effects of heavy atoms on spin centers and microstructures in SiN films produced by reactive radio-frequency sputtering in Kr-N-2 plasmas are clarified by electron spin resonance (ESR) spectroscopy and high-resolution transmission electron microscopy (HRTEM). Rutherford backscattering spectroscopy suggests that the film-constituent elements have uniform depth profiles with the atomic ratio of SiN1.21. The films produced in the Kr/N-2 = 0.5 and 2 plasmas show tripler-character ESR curves with a zero crossing of g = 2.0036. High-temperature measurements (> 400 degrees C) reveal that their ESR curves have an additional spin center at g = 2.0018, which disappears in room-temperature measurement. At 590 degrees C, the ESR curve becomes a simple featureless curve similar to the silicon KO spin center. The Kr/N-2 = 10 film exhibits a simple featureless curve with g = 2.0016, which is mainly attributed to the oxidized silicon spin centers. This film also shows a novel weak signal at g = 2.126 which disappears in vacuum. This signal probably originates from a volatile species, such as oxygen-related small radicals. ESR curves of this Kr/N-2 = 10 film measured in vacuum are unchanged up to 590 degrees C. HRTEM reveals that the fibrous voids are uniformly scattered and make the open columnar structure. These salient structures induced by heavy atom effects are consistent with the structure zone model and should be effective for strong adsorption of paramagnetic species.