A structure includes a field effect transistor (FET) stack including a plurality of transistors over a buried insulator layer. A polysilicon isolation region is in a substrate below the FET stack and the buried insulator layer. A resistor network is in the polysilicon isolation region, the resistor network having a different resistivity than the polysilicon isolation region. The resistor network may include a resistive wire having a first width and a resistive pad within the resistive wire under each FET in the FET stack. Each resistive pad has a second width larger than the first width of the resistive wire. A length of the resistive wire is different aside each resistive pad to adjust a threshold voltage of an adjacent FET in the FET stack to a predetermined value to compensate for non-linear voltage distribution between an input and an output of the FET stack.