<p>Junctionless Tunnel Field Effect Transistors (JL-TFETs) represent a significant shift in transistor design, attracting attention for their ability to achieve a steep subthreshold swing (SS) and operate at ultra-low power. Unlike conventional design, the junctionless design simplifies manufacturing, improves scalability, and reduces variations in threshold voltage. This paper analyzes different JL-TFET structures such as nanotube, pocket-doped, double-gate, and hetero-gate structures and focuses on their unique operational principles like carrier transport, band alignment, tunneling mechanisms, and performance trade-offs. Special emphasis is placed on the detrimental impact of quantum confinement (QC) and interface trap charges (ITCs), which degrade ON-current, increase leakage, and limit subthreshold swing is also discussed in this paper. Additionally, the fabrication of JL-TFETs remains highly challenging, requiring ultra-high uniform doping, nanometer-scale control of channel thickness, high-quality gate dielectrics, and abrupt band alignment—all of which critically affect device performance and are discussed in detail. Furthermore, a comparative analysis of state-of-the-art JL-TFET designs is presented, highlighting key metrics such as DC and RF performance. The study underscores the potential of JL-TFETs as next-generation transistors while identifying key material, structure, and fabrication challenges that must be addressed for their practical realization.</p>