We introduce the concept of electric-field-tailoring in MBE-grown vertical metal-oxide semiconductor field-effect transistors (MOS-FETs) and show that significant improvements in terms of supply voltage, current and speed are achievable in such MOSFETs by employing a planar-doped-barrier MOSFET (PDBFET) concept. Investigation of electrical characteristics and carrier transport in sub-100 nm channel PDBFETs shows the predicted improvements compared with classical MOSFETs.