Electrical degradation of (Ba, Sr)TiO3 (BST) thin films was investigated by annealing Pt/BST/Pt structures in D-2/N-2 and D2O-containing furnace ambients. Deuterium depth profiles were correlated to the current-voltage characteristics of the BST thin films. The dependence of the D distribution and leakage current density on the D incorporation method indicates that mobile, donor-type deuterium defects dissolve in large concentrations within BST thin films, and that their effects on leakage properties depend on the nature of their charge compensation. A mechanism is proposed for the leakage current increase after D-2/N-2 anneals, and good quantitative agreement between the theoretical results and experimental data is demonstrated. (C) 2000 American Institute of Physics. [S0003-6951(00)03335-0].