This work investigated the barrier properties of metalorganic chemical-vapor-deposited (CVD) tantalum nitride (TaN) and physical-vapor-deposited (PVD) TaN between Cu and Si. The CVD TaN film had a preferred orientation (200) with a grain size of around 60 nm, while the PVD TaN had a (111) preferred orientation with a grain size of around 20 nm, as determined by transmission electron microscopy (TEM) and x-ray diffraction (XRD) analyses. Degradation study of the Cu/ TaN/Si contact system was also performed by sheet resistance measurement, scanning electron microscopy (SEM), XRD, secondary ion mass spectroscopy (SIMS), and shallow junction diodes. These results indicated that the PVD TaN film can act as a better diffusion barrier than the CVD TaN film. The higher thermal stability of PVD TaN than CVD TaN can be accounted by their difference in microstructures. The failure mechanisms of both CVD TaN and PVD TaN films as diffusion barriers between Cu and Si were also discussed.