We have investigated the changes of chemical bonding states of an H-terminated silicon surface under inert gas (Ar,N-2) and ultrahigh vacuum (UHV) annealing using X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS). SiC is formed (corresponding to similar to0.1 monolayer) under inert gas and UHV annealing at around 500degreesC, which is coincident with the temperature of the dangling bonds formation at the silicon surface by hydrogen desorption, whereas SiC is not formed under O-2 annealing. From the precise analysis using a combination of XPS and TDS, the SiC formation is related to the reaction between the silicon surface and the organic contamination that is unavoidably adsorbed during air exposure. We also studied the electrical properties of metal oxide semiconductor capacitors with a chemical vapor deposited silicon oxide gate insulator formed on Ar- and O-2-annealed silicon surfaces. At preannealing increases the leakage current by approximately 10(-4) times compared with O-2 annealing. (C) 2005 The Electrochemical Society.