The present disclosure provides a tunnel field effect transistor (TFET) device comprising at least following segments: a highly doped drain region, a lowly doped up to undoped channel region being in contact with the drain region, the channel region having a longitudinal direction, a highly doped source region in contact with the channel region, the contact between the source region and the channel region forming a source-channel interface, a gate dielectric and a gate electrode covering along the longitudinal direction at least part of the source and channel regions, the gate electrode being situated onto the gate dielectric, not extending beyond the gate dielectric, wherein the effective gate dielectric thickness tgd,eff of the gate dielectric is smaller at the source-channel interface than above the channel at a distance from the source-channel interface, the increase in effective gate dielectric thickness tgd,eff being obtained by means of at least changing the physical thickness tgd of the gate dielectric.