A NiPt layer with a Pt atom concentration equal to 15% plus or minus 1% is deposited on a semiconductor region (which may, for example, be a source/drain region of a MOS transistor). An anneal is then performed at a temperature of 260° C. plus or minus 20° C., for a duration in the range from 20 to 60 seconds, in order to produce, from the Nickle-Platinum (NiPt) layer and the semiconductor material of said semiconductor region, an intermetallic layer. Advantageously, the intermetallic layer possesses a structure of heteroepitaxy with the semiconductor material, and includes free Pt atoms.