**Abstract:**
A thorough study of the ballistic effect on the performance of the carbon nanotube field effect transistor has been explored in detail in this paper. The behavior of CNTFETs has been analyzed as a function of temperature by varying the gate dielectric constant and gate oxide thickness. Current ratiowith a fixed oxide thickness and diameteris observedunder different temperature for different dielectric materials and the ratio is increased while increasing the dielectric constant but the ratio degrades with the increasing temperature for all dielectric materials. On the other hand, current ratio is decreased while increasing oxide thickness for a fixed dielectric material and diameter as a function of temperature. The degradation of current ratio in lower temperature range is noticeable but for higher temperature range the slope of the degradation of current ratio is almost constant. The off state current remains same regardless of varying dielectric constant and oxide thickness and always increases while increasing the temperature. Transconductance remains almost constant as a function of temperature but increases with the increase of dielectric constant for all oxide thickness for a fixed tube diameter. Transconductance slightly decreases with the increasing oxide thickness for all dielectric materials. Effect of tube diameter for the variation of band gap is also investigated which is inverse relationship.

**Keywords:**
Transconductance, Off-state current, Current Ratio, Chiral Indices, Chiral Angle.