Low-pressure chemical vapor deposition (LPCVD) Si3N4 quality presents a dramatic improvement after oxidation. Both liquid-phase anodic oxidation and rapid thermal oxidation were studied in this work. After oxidation, "SiO2''-like layers grown on the surface, and oxygen incorporated into the Si3N4 layer were observed. The nonstoichiometric bonding, i.e., Si-2=N, Si dangling bonds, and crystalline Si were oxidized into Si-2=N-O or SiO2, and the stoichiometric Si(3)equivalent toN bonding maintained a higher-k property. In addition, more oxygen replacement of the imperfect Si-N bonds after anodic oxidation contributed to better improvement in suppressing gate leakage current. (C) 2004 The Electrochemical Society.