Epitaxial growth of Ge thin films onto (100) silicon by DC-Pulsed Magnetron Sputtering was realized and proved by X-ray and electron diffraction. Transmission and high-resolution electron microscopy across the interface region directly confirmed a high degree of epitaxy and show that planar defects and threading dislocations are the relevant lattice imperfections. Electron microscopy shows that a post-deposition rapid thermal annealing process, up to 673 K, is effective to defect annihilation. The films grow single crystalline, slightly misoriented, below 0.1 degrees. A weak roughness around 0.6 nm, was measured both at the Ge-Si interface and at the film surface. The Ge films grown onto n-type Si show the rectifying electrical behaviour typical of p-type semiconductors.