Electron cyclotron resonance nitrous oxide (N2O) plasma oxidation has been investigated as a process to grow thin oxide on polycrystalline silicon and (100), (111), and (110) oriented crystalline silicon. In spite of a low thermal budget, N2O plasma oxidation incorporates nitrogen atoms at the silicon/silicon dioxide interface and forms a nitrogen-rich layer. The incorporated nitrogen atoms are tightly bound to silicon atoms at the interface with N (1s) electron energy of 397.8 eV. The oxidation rate in N2O plasma is less dependent on crystalline orientation in comparison with thermal O-2, and is therefore nearly identical in poly- and single-crystalline-Si. Polysilicon oxide (polyoxide) grown by N2O plasma oxidation exhibits better electrical properties than thermally grown oxides; this is attributed to the smooth interface between the polyoxide and a poly-Si film. Polysilicon thin film transistors fabricated with N2O plasma oxide show improved performance, which is attributed not only to the smooth interface but also to oxygen-and nitrogen-plasma passivation.