Silicon oxynitride films were deposited by plasma-enhanced chemical vapor deposition (PECVD) using nitrous oxide (N2O) and monosilane (SiH4) chemistry. A wide range of nitrogen concentrations (from 0 to 8 at. %) in silicon oxynitride film was successfully obtained by controlling PECVD deposition conditions (rf power and SiH4/N2O flow ratio). The dependence of time-dependent dielectric-breakdown (TDDB) lifetime of such films with a copper anode on these PECVD conditions can be basically explained as the nitrogen-concentration dependence of the dielectric-breakdown lifetime. Increasing the nitrogen content from zero to 6 at. % improved the TDDB lifetime of the film by about seven orders of magnitude at a TDDB test temperature of 140 degreesC. However, increasing the nitrogen concentration to over 6 at. % did not improve the TDDB lifetime; in fact, doing so degraded it. (C) 2003 American Vacuum Society.