The influences of dilute hydrofluoric acid (DHF) treatment used in wafer cleaning processes for silicon large-scale integrated circuit fabrication on thin oxide integrity was examined. Unstable current-voltage characteristics,decreased dielectric strength, and a lowering of barrier height were observed in a thin oxide (11 nm) MOS structure formed by using DHF treatment in the preoxidation cleaning procedure. Positive charges produced by some particle-related contamination, inherent to DHF treated surfaces, are related to the barrier height lowering and to the current decrease associated with electron trapping at the trap centers.