Junctionless Metal‐Oxide‐Semiconductor Field‐Effect Transistors have emerged as a promising alternative to conventional MOSFETs, offering simplified fabrication and potential performance improvements. The novelty of this research lies in the selection of hetero‐dielectric material to optimize the performance of junctionless transistors under the misaligned gate and high‐temperature conditions. Aim to explore its capability for low power high frequency application. The results reveal that the proposed junctionless FET exhibits increased transconductance (17 mS), which enables higher gain (311 dB) and diminishes capacitive effects, leading to a broader range of cut‐off frequencies (154 GHz) with gain frequency product (GFP) and gain transconductance frequency product (GTFP) is 31 THz and 95.9 THz respectively. Moreover, this research paper investigates critical reliability issues related to junctionless MOSFET, focusing on gate misalignment and thermal stability. The study reveals that gate misalignment reduces on‐current and degrades device performance. Additionally, the study examines thermal stability over a wide temperature range (300 K to 500 K), exploring the impact of temperature on performance. These valuable findings provide crucial insights to overcome fabrication challenges and drive the practical adoption of junctionless MOSFETs in future integrated circuits. To assess device performance in high‐frequency applications, Silvaco ATLAS TCAD tools are employed.This article is protected by copyright. All rights reserved.