Patent ID: 8501596

Claim:
A method comprising: forming, on a support, at least one oxidation masking layer which includes one or more holes, where the one or more holes reveal at least one Si based semi-conductor zone including inclined flanks and having a central portion and a periphery portion, said periphery portion having a thickness smaller than the central portion thickness, forming at least one Si 1-x Ge x , where 0<x, based semi-conductor zone on said at least one Si based semi-conductor zone, conducting thermal oxidation of said at least one Si based semi-conductor zone and said Si 1-x Ge x based semi-conductor zone through said masking layer so as to obtain a semi-conductor zone with a germanium concentration gradient in a direction parallel to a principal plane of said support, said germanium concentration gradient having germanium content increasing from a center to a periphery of said semi-conductor zone with the germanium concentration gradient, and etching said semi-conductor zone with the germanium concentration gradient, said etching having kinetics dependent upon a percentage of germanium in said semi-conductor zone with the germanium concentration gradient.