Various aspects include extremely thin semiconductor-on-insulator (ETSOI) layers. In one embodiment, an ETSOI layer includes a plurality of shallow trench isolations (STI) defining a plurality of distinct semiconductor-on-insulator (SOI) regions, the distinct SOI regions having at least three different thicknesses; at least one recess located within the distinct SOI regions; and an oxide cap over the at least one recess.