SiNx:H films with a wide composition range and, some of them, with low oxygen content are deposited at room temperature. The defects observed in the films are attributed to Si‐dangling bonds, with a structure depending on film composition. For the N‐rich films they are of the form ⋅Si≡(N3), whereas for the films with similar [N]/[Si] ratio but containing oxygen, the predominant defect is proposed to be ⋅Si≡(Si2O), despite of the high N content and the low O content of these films. The spin density of the films has been related to the bonds that hydrogen establishes (either Si–H or N–H), with the maximum value corresponding to the minimum hydrogen content. Both maximum and minimum values, respectively, are obtained at the silicon percolation limit of the Si–Si bonds into the SiNx:H network, x∼1.10. © 1995 American Institute of Physics.