A method for fabricating a semiconductor structure includes forming a nanosheet stack on a base. The nanosheet stack comprises one or more first nanosheet layers each comprised of a first material and one or more second nanosheet layers each comprised of a second material different from the first material. The nanosheet stack is recessed. Inner spacers comprising a third material are formed. Forming the inner spacers includes converting the first material corresponding to outer portions of each of the one or more first nanosheet layers into the third material.