Numerous silicon nitride films were prepared using different target materials (Si3N4 or Si) and different discharge gases (Ar or N-2). In the case with an Si3N4 target and Ar gas pressure (1 Pa), the N-to-Si atomic ratio of the film was stoichiometric, 1.33, even when the substrate temperature was changed considerably. When the As gas pressure was increased from 1 to 7 Pa, the nitrogen content increased while the deposition rate decreased. In the case with an Si3N4 or Si target and N-2 gas, the nitrogen content increased while the deposition rate decreased with the increase in N-2 pressure. The change in deposition rate due to the pressure was investigated using optical emission spectroscopy. X-ray photoelectron spectroscopy analysis showed that the binding energy is the same if the N-to-Si ratio was in the range from 1.33 to 1.70. It was found by X-ray diffraction analysis that crystallization occured when the substrate temperature was higher than about 1173 K.