I. Introduction
MOS transistor has been successful due to its scalability to increasingly smaller dimensions, which results in better performance. This trend still continues in accordance with Moores law and silicon-based technology has gone through a phenomenal growth in the last few decades. But, bulk MOSFET is approaching to its limiting size. Scaling down the gate length of current CMOS technology further in Nano scales causes various critical challenges and reliability issues such as increased short channel effects, reduced gate control, exponentially rising leakage current, larger process variations and high-power dissipation etc. This will reduce its potential for energy-efficient applications in near future [1]. For this reason, the semiconductor industry is looking for different materials and devices to integrate with the current silicon-based technology and, in the long run, possibly replace it. Carbon nanotube (CNT), due to its unique structure and excellent physical properties, has attracted significant attention in the field of electronics for the last few decades. CNTFET is superior in view of unique 1-D band structure, ballistic transport operation and low OFF-current properties enabling high performance and low power design [2]–[5].