The invention relates to a method for improving the mechanical strength of a ceramic matrix composite material of the SiC/SiC type, this composite material being obtained by (a) forming a fiber preform from 3rd generation silicon carbide fibers and (b) forming a ceramic matrix around the fiber preform, this ceramic matrix comprising silicon carbide. The method comprises a chemical etching treatment of the surface of the fibers by bringing said fibers into contact with a solution comprising an oxidizer, this treatment being carried out before step (a) or between steps (a) and (b).