A process for forming a semiconductor layer, especially with a view to photovoltaic applications, and more particularly to a process for forming a semiconductor layer of I-III-VI2 type by heat treatment and chalcogenization of a metallic precursor of I-III type, the process comprising: a heating step under an inert atmosphere during which the temperature increases uniformly up to a first temperature of between 460° C. and 540° C., in order to enable the densification of the metallic precursor, and a chalcogenization step beginning at said first temperature and during which the temperature continues to increase up to a second temperature, a stabilization temperature, of between 550° C. and 600° C., in order to enable the formation of the semiconductor layer. The formation of a semiconductor layer, or equivalently of an absorber, having a gain in conversion efficiency of around 4%, is thus advantageously achieved.