Ta–Zr Thin films with wide range of compositions were deposited on Si (100) substrate by co-sputtering. RF bias power from 0 to 80 W was applied during deposition. Films were then characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and four-point probe. Result showed the incorporation of Zr caused the formation of low-resistivity BCC Ta, which made the resistivity of Ta–Zr films decrease. With substrate bias increasing, the compositional range for forming amorphous structure shrank. The effects of both thermodynamics and kinetics on Ta–Zr amorphization tendency were discussed.