The present invention relates to a method for providing a Silicon-On-Insulator (SOI) stack that includes a substrate layer, a first oxide layer on the substrate layer and a silicon layer on the first oxide layer (BOX layer). The method includes providing at least one first region of the SOI stack wherein the silicon layer is thinned by thermally oxidizing a part of the silicon layer and providing at least one second region of the SOI stack wherein the first oxide layer (BOX layer) is thinned by annealing.