A tunnel field effect transistor and a method of making the same. The transistor includes a semiconductor substrate. The transistor also includes a gate located on a major surface of the substrate. The transistor further includes a drain of a first conductivity type. The transistor also includes a source of a second conductivity type extending beneath the gate. The source is separated from the gate by a channel region and a gate dielectric. The transistor is operable to allow charge carrier tunnelling from an inversion layer through an upper surface of the source.