Split-Stack Triple-Height Cell Layout for Multi-Stage CMOS

The patent applies vertical stacking to arrange multi-stage CMOS circuits in three rows along the vertical direction rather than horizontally in a single row. This dimensional change from 2D planar layout to 3D vertical stacking reduces the horizontal cell width and overall device area while keeping the circuit functionality intact through proper vertical interconnect design.

The multi-stage CMOS circuit is segmented into three distinct rows, with each row containing specific stages of the circuit. This segmentation allows independent optimization of each row's transistor placement and reduces the complexity of routing by localizing interconnects within and between rows, making the overall design more manageable.

The patent implements different transistor sizing strategies for different stages and positions within the stacked cell. Driver transistors in the first stage are sized larger to provide high drive strength, while transistors in subsequent stages are sized appropriately for their specific requirements. This local optimization ensures each transistor contributes efficiently to drive strength without unnecessarily increasing overall input capacitance.

By stacking transistors vertically in three rows, the patent enables better control over transistor gate overlap and interconnect routing. This vertical arrangement allows optimization of the electrical path lengths and reduces parasitic capacitances associated with horizontal routing, effectively managing input capacitance while maintaining drive strength through proper transistor width modulation.

The three-row vertical stacking architecture provides a structured framework that naturally minimizes interconnect lengths by placing adjacent circuit stages in vertical proximity. The standardized row-based layout with defined interconnect paths between rows reduces routing flexibility options but ensures consistently short signal paths, thereby improving signal integrity through reduced parasitic effects while maintaining sufficient layout adaptability for different circuit configurations.

The patent designs the stacked cell layout with universal interconnect structures that can accommodate different multi-stage CMOS circuit configurations. The standardized row interfaces and interconnect patterns allow the same physical layout to support various circuit functionalities, providing layout flexibility at the system level while maintaining short interconnect lengths within the standardized structure.