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Negative bias temperature instability (NBTI) degradation and recovery have been investigated for 7-50-nm non-nitrided oxides and compared to thin 1.8- and 2.2-nm nitrided oxides from a dual work function technology. A wide regime of stress fields from 2.5 to 10 MV/cm has been covered. Thermal activation has been studied for temperatures from 25 degC to 200 degC. The NBTI effect for the nitrided oxide is larger than for non-nitrided oxides. The percentage of threshold shift V th which is ldquolostrdquo during a long measurement delay-which is the quantity leading to curved V th versus stress-time curves and to errors in extrapolated lifetimes-is about equal for nitrided or thick non-nitrided oxides. The fraction of recovered V th is strongly dependent on stress time but only weakly dependent on stress field. Recovery in thick oxides leads to exactly the same problems as for non-nitrided oxides, and clearly, a fast measurement method is needed. The effect of short-term threshold shifts has been studied for extremely short stress times down to 200 ns.