After discovering the carbon nanotube (CNT) by Aijima, scientific research about this structure are expanded due to its excellent electronic properties. One of the important properties of this structure is quasi-ballistic transport with very high carrier mobility. Using carbon nanotube, two types of field effect transistors have been discussed. The first type is Schottky barrier carbon nanotube field effect transistor (SB-CNTFET) and second type is MOSFET-like CNTFETs (MOSCNTs). The MOSCNT was more favorable because of the high on-off current ratio, but leakage current (IL) of this transistor is very high because of electron band-to-band tunneling (BTBT). In order to deal with this problem, some solutions such as drain and source with a linearly or lightly doped, source and drain extensions and asymmetric oxide thickness, have been proposed. Also, the dual material gate structure and the source and drain parameters effect on the characteristics of CNTFET are investigated. Moreover, th ...