This work investigates the interaction of Pt/HfO2/Si nanometric film structures with deuterium gas (H-2(2)) at 500 degrees C, simulating the hydrogen passivation step commonly applied to metal-oxide-semiconductor devices. Selective chemical etching of Pt and HfO2 combined with H-2 detection by nuclear reaction analysis allowed quantification and depth profiling of H-2 incorporated into the structures. The presence of the top Pt layers does not measurably affect H-2 amounts incorporated underneath. However, similar to 10(14) H-2 cm(-2) are trapped at the Pt/HfO2 interfaces. This interfacial H-2 trapping implies that conventional H-2 passivation annealing can substantially influence the chemistry of metal-HfO2 interfaces.