According to an embodiment, a method of manufacturing a group III-V semiconductor device includes forming a gate contact that includes an electrode stack including a first titanium layer, an aluminum layer over the first titanium layer, and a second titanium layer over the aluminum layer, and forming a biased reactive capping layer over the second titanium layer. The biased reactive capping layer includes biased reactive titanium nitride. The gate contact is a gate electrode that makes Schottky contact with the group III-V semiconductor device.