In this work we demonstrate that in MOS devices the reliability of ultrathin (< 100Å) gate oxide is a strong function of growth conditions, such as, temperature and the growth rate. In addition, for constant current gate injection the degradation of SiO2 is enhanced as the thickness is reduced. We attribute this to physical stress in SiO2 resulting from the growth process. The degradation is always more for those growth conditions which result in higher physical stress in SiO2. Higher temperatures and slower oxidation rates allow stress relaxation through viscous flow and hence result in SiO2 of better reliability. We also found that for constant current stressing, the interface damage is more at the collecting electrode than at the injecting electrode. ΔDit (stress induced interface state generation) can be reduced after a high temperature Ar post anneal after the gate oxide growth.