In this paper, we report the effects of a N2 postmetallization annealing (PMA) on the reliability and charge-trapping characteristics of tungsten/ La2 O3 /silicon structures. The samples are stressed with a constant-voltage stressing (CVS) with substrate injection. After the stressing we found that the flatband voltage (VFB) of the samples positively shifts, indicating a net negative charge trapped in the La2 O3 and its interfaces. Samples with PMA exhibit less VFB shift after the stressing as compared to postdeposition annealing La2 O3 films. Moreover, La2 O3 with PMA at higher temperatures increases the endurance to VFB shift, but the equivalent oxide thickness (EOT) of the metal-insulator- semiconductor capacitors increases; thus, a trade-off between higher endurance to charge trapping and low EOT is required. The reliability and electrical characteristics of La2 O3 films are to some extent sensitive to the annealing conditions and timing within the process flow.