Metal Gate Stack Structures for Scaled GAA Semiconductor Devices

The fabrication process is divided into multiple discrete stages including forming first and second trenches at different depths, selective epitaxial growth in specific regions, and staged doping processes. This segmentation allows complex operations to be broken down into manageable steps that can be executed with existing manufacturing capabilities while achieving advanced device structures.

The patent introduces vertical dimensionality by forming trenches at different depths (first trench extending to first depth, second trench extending to second depth greater than first depth) and creating multi-layered semiconductor structures through selective epitaxial growth. This vertical stacking enables increased functional density without proportionally increasing lateral processing complexity.

The patent applies different processing conditions to different regions of the substrate: first trench is formed in first region with specific doping, second trench is formed in second region with different doping concentrations and depths. Selective epitaxial growth is performed only in designated regions. This local differentiation allows optimization of each region for its specific function while maintaining overall process reliability through standardized fabrication techniques.

The patent incorporates buffer regions and transition zones between differently doped areas, and uses intermediate processing steps such as selective removal of sacrificial layers and staged epitaxial growth. These cushioning measures prevent defect propagation and process variability from compromising overall device reliability, allowing smaller feature sizes to be manufactured with maintained yield.