The charge-pumping measurement technique was successfully applied to submicron (Leff = 0.35 μm) n-MOSFETs on ultra-thin (50 nm) SOI film. The hot-carrier-induced degradation is studied by examining the damages to both gate-oxide and buried-oxide (BOX) interfaces. We found that when stressed at maximum substrate current, interface-trap generation is still the primary cause for hot-carrier-induced degradation. Even for ultra-thin-film SOI devices, the hot-carrier-induced damage is locally confined to the gate-oxide interface and only minor damage is observed at the buried-oxide interface. The buried-oxide interface charging contributes less than 5% of the overall drain current degradation.