This book employs the FETToy code to investigate and compare the electrical characteristics of carbon nanotube field-effect transistors (CNT-FETs) and silicon nanowire field-effect transistors (SiNW-FETs) utilizing SiO2, ZrO2, and HfO2 as dielectric materials. The objective is to discern the impact of dielectric choices on the performance of these nanoscale transistors. The dielectric materials (SiO2, ZrO2, and HfO2) are systematically varied to understand their influence on device behavior. Results indicate that the choice of dielectric profoundly affects the electrical performance of both CNT-FETs and SiNW-FETs. The study unveils nuanced relationships between dielectric properties and transistor characteristics, shedding light on the suitability of SiO2, ZrO2, and HfO2 in optimizing device performance. Furthermore, the investigation explores the unique attributes of CNT-FETs compared to traditional SiNW-FETs, providing insights into the potential advantages and challenges associated with the integration of carbon nanotubes in transistor design. The findings of this analysis contribute valuable knowledge for the ongoing development of nanoscale transistors.