Based on the nonequilibrium Green’s function (NEGF) ballistic transport simulation, an optimized homojunction carbon nanotube (CNT) gate-all-around tunnel field effect transistor (GAA TFET) is proposed in this study. This TFET enhances the ON-state current and suppresses the ambipolarity extensively. By changing the channel diameter, gate length, and insulator thickness along with different values of doping levels and dielectrics of the source/channel/drain regions, a subthreshold swing $({SS})$ equal to ${11} ~\text {mV}/\text {dec}$ with an ON/OFF ratio of 108 is obtained at ${V}_{G}={V}_{D}={0.4}$ V. Source (drain) underlap/overlap with the gate is also considered in reaching an optimum result. Such advantages can be followed on other 1-D TFET devices and are explained in detail on the energy band diagram of the device.