Graphene- and/or carbon nanotube-based radiation-hard transistor devices and techniques for the fabrication thereof are provided. In one aspect, a method of fabricating a radiation-hard transistor is provided. The method includes the following steps. A radiation-hard substrate is provided. A carbon-based material is formed on the substrate wherein a portion of the carbon-based material serves as a channel region of the transistor and other portions of the carbon-based material serve as source and drain regions of the transistor. Contacts are formed to the portions of the carbon-based material that serve as the source and drain regions of the transistor. A gate dielectric is deposited over the portion of the carbon-based material that serves as the channel region of the transistor. A top-gate contact is formed on the gate dielectric.