SiNx and AlNx films were both DC- and RF-magnetron reactively sputtered at various deposition powers and total bleeding pressures as a function of flow rate ratio of Ar to N-2(F = f(Ar)/fN(2)) The microstructure of the SiNx films is amorphous. A low F results in a smooth and featureless morphology in the RF-magnetron sputtered SiNx films. However, microvoids are present in these films when Fis increased. DC-magnetron sputtered SiNx films produce a porous structure as well as a rough surface at a low F, but the porosity of the films appears to be decreased with increasing F. On the other hand, AlNx films consist of small and randomly oriented hcp crystals. In the RF-magnetron sputtered AlNx films, the density of microvoids is high at a low F but is decreased with an increase of F and the deposition rate. In contrast, the density of microvoids is increased with increasing F and the deposition power for the DC-magnetron sputtered AlNx films.