It is demonstrated that the thickness limit of a thin nitride film which can withstand reoxidation is reduced to about 3.5 nm when it is depositedinsituon a thin‐deposited oxide film. The deposited oxide apparently provides a better surface for nitride nucleation and initial growth. Using this finding an oxide‐nitride‐oxide (ONO) film as thin as 4.6 nm was fabricated and shown to have good electrical properties and low defect density. The current leakage through the film was close to the acceptable limit in dynamic‐random‐access‐memory technology. It was also found that electron trapping is substantially higher in ONO films produced by reoxidation than in films having a top deposited oxide.