Endurance considerations induced by the degradation of top and bottom oxides are proposed for a SONOS memory. First, a correlation is found between the widespread C-V curves induced by interface generation and cycling numbers (cyc. #). Unlike VFB (accumulation region), VT (inversion region) shows a much severe shift. Interface state (Nit) is identified as a key factor even when a 2nm bottom oxide is used. Moreover, charge to breakdown (QBD) for an ONO capacitor under positive and negative constant current stress (CCS) is investigated. Our study reveals that QBD of such stacks strongly depends on the top oxide thickness. A field enhancement induced by charges in a trapping nitride layer is the root cause. Based on Weibull statistics, the risk of dielectric breakdown for both blocking layers is then evaluated.