We report on the characterization of silicon-rich nitride (SRN) and silicon-rich oxynitride (SRON) films used in poly-Si gate patterning. SRON and SRN films were deposited by plasma-enhanced chemical vapor deposition in a commercial 200 mm. reactor. Film composition was measured using Rutherford backscattering, and hydrogen concentration was determined using helium forwardscattering spectroscopies. For a typical SRON film, the atomic percentages of Si/O/N/H were similar to 40/30/10/20, while a typical SRN film had Si/N/H of similar to 40/35/25. Blanket films of 3000-4000 Angstrom thickness were characterized optically using Fourier-transform infrared (FTIR) spectroscopy over 400-4000 cm(-1), and showed evidence for significant Si-Si, Si-H, and N-H bonding. Additional characterization using variable-angle spectroscopic ellipsometry over the range of 140-1000 nm, to obtain optical constants for lithography modeling, will be reported in a future article. The significant H content and Si-Si bonding of the SRN and SRON films gives rise to optical absorption in the films below 500 nm that enables their use as antireflection layers.