A method of making a silicon-germanium film has variable germanium content

The substrate (1) is provided with a first semiconductor region (2) partially covered by a first gate pattern (3) to define a protected surface (2b) and an open surface (2a). A continuous layer of silicon-germanium (6) is non-selectively deposited on the first semiconductor zone (2) and the first grid pattern (3). The continuous layer of silicon-germanium (6) forms an interface with the first semiconductor region (2). Diffusion annealing / condensation is carried out to diffuse the atoms of germanium from the layer of silicon-germanium (6) to the open surface of the first semiconductor zone (2).