The kinetics of growth of a nanosized germanium film deposited by magnetron sputtering on the Si(001) surface is studied using a developed experimental X-ray reflectometry technique distinguished by the joint recording of specularly reflected and diffusely scattered radiation. By using this technique, it is possible to perform in situ both the analysis of the morphology of the growing film and the control of its thickness with an accuracy to 1 nm. Dependences of the intensity of specular reflection, diffuse scattering, rate of growth, and mean square roughness and density of the film on the deposition time are obtained. According to the results of the measurement of specularly reflected radiation, the film roughness increases with time according to a power law. However, at a thickness of the film of 4 nm, a clearly defined maximum of diffuse scattering is observed, the angular position of which corresponds to the critical angle of total external reflection of germanium of 0.31°. This pattern of distribution of scattered radiation is explained by the manifestation of the Yoneda effect that consists in the anomalous X-ray scattering, the maximum of which corresponds to the critical angle θC of total external reflection from the film. It is established experimentally that, at the initial stage of growth, the film is formed by the Volmer–Weber mechanism. It is found using in situ X-ray reflectometry that the formation of a continuous layer of a germanium film occurs at its thickness of 7 nm; the subsequent growth of the film proceeds according to the power law σf ~ tβ, where β = 0.23.