The disclosure provides a field effect transistor (FET) stack with methods to form the same. The FET stack includes a first transistor over a substrate. The first transistor includes a first active semiconductor material including a first channel region between a first set of source/drain terminals, and a first gate structure over the first channel region. The first gate structure includes a first gate insulator of a first thickness above the first channel region. A second transistor is over the substrate and horizontally separated from the first transistor. A second gate structure of the second transistor may include a second gate insulator of a second thickness above a second channel region, the second thickness being greater than the first thickness. A shared gate node may be coupled to each of the first gate structure and the second gate structure.