Process for thinning the active silicon layer of a substrate of "silicon on insulator" (soi) type

A method for thinning an active silicon layer of a silicon-on-insulator (SOI) substrate having an insulator layer buried between the active silicon layer and a support, the method comprising:

• forming a sacrificial silicon oxide layer by sacrificial thermal oxidation of a portion of the active silicon layer;
• forming a complementary oxide layer on the active silicon layer using an oxidizing plasma, the complementary oxide layer having a thickness profile at least substantially complementary to a thickness profile of the sacrificial silicon oxide layer such that a sum of the thicknesses of the complementary oxide layer and the sacrificial silicon oxide layer are at least substantially constant over the entire surface of the SOI substrate;
• and
• removing the sacrificial silicon oxide layer;
• and
• removing the complementary oxide layer;
• wherein the thinned active silicon layer has an at least substantially uniform thickness after forming and removing each of the sacrificial silicon oxide layer and the complementary oxide layer.