A process is disclosed for manufacturing a film that is a smooth and has large nitride grains of a diffusion barrier material selected from a group consisting of tungsten alloys of Group III and Group IV early transition metals and molybdenum alloys of Group III and Group IV early transition metals. The diffusion barrier material is preferably selected from a group consisting of ScyMz, ZryMz, ZrvScyMz, ZrvNbYMz, ZruScvNbyMz, NbyMz, NbvScyMz, TiyMz, TivScyMz, TivNbyMz, and TivZryMz, where M is one of tungsten and molybdenum. Under the process, a nitride of the diffusion barrier material is deposited by physical vapor deposition in an environment of nitrogen. The nitrogen content of the environment is selected at an operating level wherein primarily the diffusion barrier material is sputtered with between about 4×108 to about 4×1015 nitride nuclei of the diffusion barrier material per cm2 of the diffusion barrier material, where the nitride nucleation of diffusion barrier material is evenly distributed. A grain growth step is then conducted in a nitrogen environment to grow a film of large nitride grain of the diffusion barrier material. Also disclosed is a stack structure suitable for MOS memory circuits incorporating a lightly nitrided refractory metal salicide diffusion barrier with a covering of a nitride of a diffusion barrier material. The stack structure is formed in accordance with the diffusion barrier material nitride film manufacturing process and exhibits high thermal stability, low resistivity, long range agglomeration blocking, and high surface smoothness.