A semiconductor device includes a semiconductor substrate, a first pair of FET (field effect transistor) gate structures separated by a first gate canyon having a first gate canyon spacing, disposed upon the semiconductor substrate, a second pair of FET gate structures separated by a second gate canyon having a second gate canyon spacing, disposed upon the substrate, a first S/D (source/drain region disposed in the first gate canyon, a second S/D region disposed in the second gate canyon, a first BDI (bottom dielectric isolation) element disposed below the first S/D region and having a first BDI thickness, and a second BDI element disposed below the second S/D region and having a second BDI thickness. The first BDI thickness exceeds the second BDI thickness.