Some properties of thin oxides (< 15 nm) are different from those of the thicker ones. The structure and refractive index of such thin oxides have dramatic thickness dependence. The interfacial layer also has a different structure at such a thickness. Trap origins have been studied and methods of elimination were discussed in which the tradeoff correlation between the density of electron traps and hole traps was presented. Current topics, related to devices studied in our laboratory, including oxides between poly/Si in a BiCMOS structure, electron trapping of LDDnMOS and thin ONO multi-layers structure are also discussed.