We propose a method within density functional theory for aligning defect energy levels at interfaces without relying on experimental data. We apply our scheme to the alignment of charge transition levels of the interstitial hydrogen and the hydrogen bridge defect (-Si-H-Si-) at the Si-SiO2 interface. We find that the +/- charge transition level of the interstitial hydrogen is located in the upper part of the silicon band gap. The defect level alignment obtained in our scheme supports that the hydrogen bridge defect may play an important role in stress-induced leakage current generation, as proposed previously. (c) 2007 Elsevier B.V. All rights reserved.