The characteristics of atomic layer deposited (ALD)-Al2O3 gate dielectrics with CF4 plasma surface treatment have been studied in this paper. Fluorine atoms were observed to be incorporated at bulk Al2O3 and pile-up at both Al/Al2O3 and Al2O3/Si interfaces. X-ray photoelectron spectroscopy analysis demonstrated that Al-O bonds were replaced by Al-F and F-Al-O bonds as samples were treated in CF4 plasma. A physical model was proposed to explain the capacitance-equivalent-thickness (CET) degradation and capacitance-frequency-dispersion phenomenon. The CF4 plasma-treatment approach can immunize capacitance dispersion due to its excellent capability of interface trap passivation by fluorine atoms in Al2O3 dielectrics. Fluorine incorporation was proven to improve the Al2O3 dielectric characteristics of hysteresis, oxide reliability, and capacitance dispersion. (C) 2007 The Electrochemical Society.