The increasing need of miniaturization, functionality, performance, and low cost have been the attractive force towards the use of high-k dielectrics as they provide crucial functions in integrated circuit as gate dielectrics, with their performance demands becoming more and more stringent as feature sizes decrease and speeds rise. This study investigates the impact of high-k dielectric materials on the electrical performance of Carbon Nanotube Field Effect Transistors (CNTFETs) using the Field Effect Transistor Toy (FETToy) simulator. Six gate dielectrics; SiO₂ , Al₂ O₃ , Y₂ O₃ , Ta₂ O₅ , HfO₂ , and La₂ O₃ were evaluated under identical structural conditions, including a 1nm nanotube diameter, 1.5nm gate oxide thickness, and 1V drain bias at 300K. The simulation focused on key performance parameters such as drain current (Id), quantum capacitance (Cq), carrier velocity, mobile charge, quantum-to-insulator capacitance ratio (Cq/Cins), and transconductance-to-current ratio (gm/Id). Results show that the use of high-k dielectric material significantly enhances the drain current, carrier velocity, and charge density, indicating improved gate coupling and electrostatic control. Among all the evaluated materials, La₂ O₃ exhibited superior performance with the highest ON-current (77.5 µA), greatest carrier velocity (5.92 × 10⁶ cm/s), and strongest gate control, while SiO₂ showed the weakest behavior across most metrics with lowest ON-current (30µA), lowest carrier velocity(4.2×106cm/s) and lowest value of 4.46×106 mobile charge/(q/cm). The analysis further reveals the need for balanced dielectric selection to optimize switching speed and energy efficiency. These findings confirmed that La₂ O₃ is a promising dielectric for high-performance CNTFET applications in the next-generation nanoelectronic circuits.