We present the evolution of surface stress of Si (100) at the oxide film thickness from 0 to 5 nm. Using micromechanical cantilevers, we have measured surface stress evolution during plasma oxidation with applying positive bias to the samples and observed five stages in surface stress. The stress curve depending on oxidation time showed a quick buildup of compressive stress, followed by a tensile stress formation, gradually changed to tensile one and compressive stress appeared again. In the second stage, the formation of tensile stress suggests a oxygen-bridged dimer structure. Only the last compressive stress have been known as a intrinsic stress in silicon oxide film of 10 nm to 1000 nm, which due to the lattice mismatch of Si and SiO2. For the cases of oxidation with applying negative biases, stress curves showed different time dependence from that with positive bias. They showed three stages, the first two stages which were observed in the case of positive bias did not appear.
