A method may include providing a silicon-on-insulator (SOI) substrate, the SOI substrate comprising an insulator layer and a silicon layer. The silicon layer may be disposed on the insulator layer, where the silicon layer comprises a first silicon thickness variation. The method may include forming an oxide layer on the silicon layer, where the oxide layer has a uniform thickness. The method may include selectively etching the oxide layer on the silicon layer, wherein the oxide layer comprises a first non-uniform oxide thickness. After thermal processing of the SOI substrate in an oxygen ambient, the non-uniform oxide thickness may be configured to generate a second silicon thickness variation in the silicon layer, less than the first silicon thickness variation.