Bandgap engineering in semimetal nanowires can be utilized to form a field effect transistor (FET) near atomic dimensions and eliminates the need for doping in the transistor's source, channel, or drain. For sufficiently small wire diameters the metallic behaviour of the semimetal is lost and a bandgap is induced. Using a full quantum mechanical description of the semimetal nanowires, we were able to demonstrate the design of a dopant-free, monomaterial confinement modulated gap transistors (CMGTs) which unlike conventional FETs do not require dopant atoms to define different device regions. This overcomes a primary obstacle to fabricating sub-5 nm transistors, enabling aggressive scaling to near atomic limits