SiN, films were prepared by rf reactively sputtering. The refractive index of SiN, films was affected by total pressure and sputtering power. When the total pressure increased, the refractive index decreased. The reduction of sputtering power showed similar effect to raise the total gas pressure. The residual stress and roughness of SiN, films depended on the total pressure, sputtering power, and the thickness. The thermal cycles may result in irreversible change of residual stress of SiNx film. The magnetic properties of TbFeCo depended on the residual stress and roughness of SiNX in the trilayer SiN,/TbFeCo/SiN, samples. The coercivity of TbFeCo was enhanced in the samples with SiN, films having low stress and large rouglmess.