The electronic and structural properties at the Ge/GeO2 interface are addressed through a density-functional simulation scheme, which includes the use of hybrid functionals for achieving defect levels and band gaps comparable to experiment. The present work discusses the determination of the germanium dangling bond levels, the band alignment in a model structure of the Ge/GeO2 interface, the thermodynamics of GeOx, the stability of the oxygen vacancy across Ge/GeOx/HfO2 stacks, the structural and electronic properties of GeOx, and its ability to trap electrons. ©The Electrochemical Society.