<p>Complementary metal-oxide-semiconductor (CMOS) integrated circuits operating at (sub) terahertz frequencies ranging from 0.1 through 10 THz are of increasing importance, with applications spanning from sensing to ultrahigh-speed communications. Notably, exceptional data rates are expected in the deployment of terahertz technology for future 6G wireless communications-enabled Industrial Internet of Everything to transcend the threshold of the 5th Industrial and Technological Revolution. Nevertheless, despite the gradually closing detector technology gap between classical microelectronics and optoelectronics a major unmitigated shortcoming is the hitherto lack of an established design environment or technique to develop commercial THz CMOS circuits. Our study delves into the physical principles and engineering techniques germane to the metal-oxide-semiconductor field-effect transistor-based THz direct detector at room-temperature operation. By exploring and tackling the contemporaneous technical and economic barriers that hinder industrial-scale production of low-cost THz devices, this research aims to identify current process design kit deficiencies from CMOS foundries, uncover design rules, and recommend optimization schemes via the inherent phenomena of the direct detection mechanism, technology compatibility, and figures-of-merit. Ultimately, the goal is to develop a low-cost, compact THz detector capable of achieving high-performance room-temperature operation. This entails meticulous investigation of key aspects such as high sensitivity, low noise, and electrical (voltage) responsivity, all of which collectively engender the actualization of state-of-the-art device and circuit parameters.</p>