In semiconductor devices, integrity of a titanium nitride material (152) may be increased by exposing the material to an oxygen plasma (110) after forming a thin silicon nitride -based material. The oxygen plasma (110) may result in an additional passivation of any minute surface portions which may not be appropriately covered by the silicon nitride-based material. Consequently, efficient cleaning recipes, such as cleaning processes (111) based on SPM, may be performed after the additional passivation without undue material loss of the titanium nitride material (152). In this manner, sophisticated high-k metal gate stacks may be formed with a very thin protective liner material on the basis of efficient cleaning processes without unduly contributing to a pronounced yield loss in an early manufacturing stage.