This chapter explores the integration of MEMS/NEMS with CMOS technology, highlighting its potential to revolutionize various fields by merging micro/nano-electro-mechanical systems with CMOS circuits on a single chip. This integration allows for simultaneous use of mechanical, electrical, and nanoscale components, enabling the development of sophisticated systems. MEMS/NEMS with CMOS enhances sensitivity, precision, miniaturization, and power efficiency while improving signal processing. The fabrication process involves CMOS circuitry creation, followed by the addition of MEMS/NEMS structures, leading to compact and high-performance systems. Applications span biosensors, RF MEMS for wireless communication, nano-optics, and nanomechanical resonators for high-frequency oscillators. Additionally, CMOS-based MEMS/NEMS systems have gained prominence in sensor applications such as gas sensors, biosensors, and pressure sensors. While CMOS technology remains the most commercialized for its scalability and performance, new technologies like CNTFET, Nanowire FET, Nanosheet FET, and TFET are being explored to address the limitations of MOS technology at smaller scales. MEMS sensors stand out for their lightweight, portability, low cost, low power consumption, and high sensitivity, making them vital for modern systems and advanced analysis. This integration is set to play a crucial role in the development of beyond-Moore devices and future technological innovations.