It is demonstrated that monolayers of organic molecules (long chain hydrocarbons) as thin as 1.9 nm, deposited by the self‐assembly technique on silicon, form high performance electrically insulating barriers. Their properties are compared with those of silicon dioxide. Leakage current densities through the organic monolayers of the order of 10−8–10−7A/cm2have been obtained. These values are 4–5 decades lower than those for silicon dioxide of equivalent thickness. Larger tunneling barriers for organic monolayers than for silicon dioxide explain these results. ©1996 American Institute of Physics.