TaN and Ta/TaN films deposited by commercial self-ionized plasma system have been characterized by X-ray diffraction (XRD) patterns, transmission electron microscopy (TEM), and Auger electron spectroscopy (AES). Based on the results of XRD patterns, increasing the N concentration of TaN under-layer enhances the crystallization of over-deposited alpha-Ta film. According to the observations of XRD patterns and TEM images, the crystalline property of over-deposited alpha-Ta film is affected by the thickness of underlying TaN film when the underlying TaN possesses sufficient N concentration. Thickening underlying TaN film is favorable for the crystallization of upper alpha-Ta film. The analyses of AES depth profiles indicate that the influence of TaN thickness on the crystal growth of upper alpha-Ta film results from the intermixing region between TaN film and substrate. The intermixing region is likely induced by naturally sputtering bombardment. The expansion of the intermixing region is modifiable with the adjustment of TaN deposition conditions. Suppressing the intermixing region can reduce the TaN-thickness effect on the formation of subsequent alpha-Ta crystals. (C) 2016 Elsevier B.V. All rights reserved.