For LOCOS application, silicon nitride (SiNx) insulators have been deposited by ECR-CVD at room temperature and with N-2 flows of 2.5, 5, 10 and 20 sccm on pad-SiO2/Si or on Si substrates. The obtained SiNx/Si structures were used to analyze the SiNx characteristics. FTIR analyses reveal the presence of Si-N and N-H bonds. The refractive indexes between 1.88 and 2.48 and the thickness between 120 and 139 nm were determined by ellipsometry. With these thickness values, the deposition rates of 9.6-10.1 nm/min and the BHF etch rates of 2-86 nm/min were determined. On the SiNx/pad-SiO2/Si structures, the LOCOS process was performed. Optical and SEM microscopy analyses were used to investigate the SiNx resistance to thermal oxidation, made at 1000 degreesC, and the bird's beak in the obtained LOCOS structures, respectively. These analyses reveal that SiNx insulator performed with N-2 flows higher than 2.5 sccm presented high quality to LOCOS isolation technology. (C) 2003 Elsevier Science B.V. All rights reserved.