An ammonia-free method of depositing silicon nitride by way of plasma-enhanced chemical vapor deposition (PECVD). Source gases of silane (SiH4) and nitrogen (N2) are provided to a parallel-plate plasma reactor, in which energy is capacitively coupled to the plasma, and in which the wafer being processed has been placed at a support electrode. Low-frequency RF energy (e.g., 360 kHz) is applied to the support electrode; high-frequency RF energy (e.g., 13.56 MHz) is optionally provided to the parallel electrode. Process temperature is above 350° C., at a pressure of about 2.5 torr. Any hydrogen present in the resulting silicon nitride film is bound by N—H bonds rather than Si—H bonds, and is thus more strongly bound to the film. The silicon nitride can serve as passivation for ferroelectric material that may degrade electrically if contaminated by hydrogen.