In this work the authors have focused on Carbon Nanotube (CNT) and Carbon Nanotubes Field Effect Transistors (CNTFETs). In every 18 months the number of transistors in an integrated circuit doubles according to Moore's law. This increased number of transistors means the size of transistors will decrease as a result of which the circuit size decreases. As the size of the transistor decreases below 10 nm, the traditional MOSFETs show multiple limitations, thereby leading to the development of CNTFETs in order to replace these MOSFETs. For CNTFETs, the quantum capacitance plays a major role in deciding the gate capacitance. The band gap of CNT is inversely proportional to the diameter of carbon nanotube. The saturation current increases when dielectric constant value increases. In this paper, it is studied that the nano-scale domain CNTFETs devices are better compare to MOSFETs due to their reduced quantum capacitance. © 2017 IEEE.