During evaluation of negative bias temperature instability (NBTI) in short-channel devices, we found that using an optimized nitrogen depth profile is important in suppressing NBTI when scaling down CMOS devices. Performing the NO anneal process before oxidation yeilds good transistor performance, suppressing NBTI by 25%. When using more nitrogen to moderate gate leakage and boron penetration, in addition to the amount of nitrogen, it is important to control the depth profile of the nitrogen on gate insulator, as our research shows that the interface peak concentration of nitrogen enhances NBTI degradation.Index Terms-Gate insulator, MOSFET, negative bias temperature instability (NBTI), nitrogen depth profile, NO annealing, SiO2.