Semiconductor structures including parallel graphene nanoribbons or carbon nanotubes oriented along crystallographic directions are provided from a template of silicon carbide (SiC) fins or nanowires. The SiC fins or nanowires are first provided and then graphene nanoribbons or carbon nanotubes are formed on the exposed surfaces of the fin or the nanowires by annealing. In embodiments in which closed carbon nanotubes are formed, the nanowires are suspended prior to annealing. The location, orientation and chirality of the graphene nanoribbons and the carbon nanotubes that are provided are determined by the corresponding silicon carbide fins and nanowires from which they are formed.