A vertical-mode tunnel field-effect transistor (TFET) is provided with an oxide region that may be laterally positioned relative to a source region. The oxide region operates to reduce a tunneling effect in a tunnel region underlying a drain region, during an OFF-state of the TFET. The reduction in tunneling effect results in a reduction or elimination of a flow of OFF-state leakage current between the source region and the drain region. The TFET may have components made from group III-V compound materials.