For realizing highly reliable Cu wiring in 3D/2.5D-IC, SiNx films formed by the reactive sputtering deposition and the plasma-enhanced chemical vapor deposition (PECVD) at low substrate temperatures are characterized and compared by use of X-ray reflectivity (XRR), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR). The film density obtained by XRR shows clear difference between the sputtering and PECVD films. Si-H bonding concentrations obtained by analyzing FT-IR spectra show good correlations with the film densities independent of deposition methods and conditions. Lower density properties of PECVD films could be attributed to higher density of residual Si-H bonds in the films.