Tantalum pentoxide thin films were prepared by plasma enhanced chemical vapor deposition, using a TaF5 source and a microwave excited H-2/O-2 plasma. The thickness and the density were determined by grazing incidence x-ray scattering, and confirmed by ellipsometry and Rutherford backscattering spectroscopy. Surface roughness measurements by atomic force microscopy and by x-ray scattering differ but suggest the average roughness (rms) is typically 0.28 nm for the amorphous phase and <0.83 nm for the crystallized form.