CFET

**CFET (Complementary FET) 3D Stacking** is **a three-dimensional semiconductor integration technique where NMOS and PMOS transistors are vertically stacked in close proximity, sharing a common gate structure and minimizing parasitic elements through direct vertical interconnection — enabling dramatic area reduction and improved performance density**. CFET technology represents a fundamental paradigm shift from traditional planar and FinFET layouts by converting the lateral CMOS device pairs into vertically stacked structures, allowing chip area reductions of 40-50% compared to conventional arrangements while maintaining or improving electrical performance. The CFET structure places NMOS transistors above PMOS transistors (or vice versa) with a shared gate that simultaneously controls both device types, while independent source-drain regions maintain electrical isolation between devices through careful junction engineering and isolation structures. This vertical integration dramatically reduces parasitic capacitance between complementary device pairs, enabling faster switching speeds, reduced dynamic power consumption, and improved noise margins compared to laterally-spaced CMOS pairs. Fabricating CFET structures requires precise control of multiple sequential epitaxial growth steps to deposit alternating layers of silicon with different dopant types, followed by sophisticated patterning and etching processes to define individual channel regions while maintaining electrical isolation between adjacent devices. Gate work function engineering becomes critically important in CFET technology, as a single gate structure must simultaneously optimize threshold voltages for both NMOS and PMOS transistors, requiring careful selection of gate metal materials and alloys to achieve symmetric device characteristics. CFET architectures enable significantly improved power delivery efficiency by placing power and ground connections closer to the active devices, reducing resistive losses in interconnect networks and enabling smaller decoupling capacitor networks. The co-location of complementary device pairs simplifies power distribution routing and enables more efficient circuit design topologies, particularly for logic gates and standard cells. **CFET 3D stacking represents a revolutionary approach to semiconductor scaling, delivering dramatic area reductions and improved power efficiency through vertical integration of complementary device pairs.**