Processing of synthesis $Si_3N_4$ UFP in the RFCVD reactor, using $SiCl_4$ and $NH_3$ as precursors, were experimentally researched. The influence of some operation parameters on the properties of products was investigaed. The nanostructured material made of such $Si_3N_4$ particles was fabricated under highpressure. The results of experiments indicated that it differed from the materials made of coarse $Si_3N_4$ powder on some electric properties.