Disclosed are embodiments of a field effect transistor (FET) and, more particularly, a fully-depleted, thin-body (FDTB) FET that allows for scaling with minimal short channel effects, such as drain induced barrier lowering (DIBL) and saturation threshold voltage (Vtsat) roll-off, at shorter channel lengths. The FDTB FET embodiments are configured with either an edge back-gate or split back-gate that can be biased in order to selectively adjust the potential barrier between the source/drain regions and the channel region for minimizing off-state leakage current between the drain region and the source region and/or for varying threshold voltage. These unique back-gate structures avoid the need for halo doping to ensure linear threshold voltage (Vtlin) roll-up at smaller channel lengths and, thus, avoid across-chip threshold voltage variations due to random doping fluctuations. Also disclosed are method embodiments for forming such FETs.