The improvement of forming gas anneal (10 % H-2 in N-2) at 400 degrees C on electrical properties of Ge/GeOx/Tm2O3/HfO2 gate stacks is investigated. It is found that forming gas anneal effectively suppresses fixed charge density, oxide trap density and interface state density. Hydrogen is demonstrated to efficiently passivate the negative fixed charge density and reduce the global variability of the Hatband voltage down to 90 mV over a safer. A forming gas anneal is also found to reduce equivalent oxide thickness in scaled gate stacks.