Stacked Nanosheet Channel Structure for Leakage and Width Control

The patent transitions from conventional planar (2D) fabrication to three-dimensional vertical structures. Fin structures are formed by etching trenches into the substrate and filling them with semiconductor material, creating vertical channels that increase device density without proportionally increasing footprint area. This dimensional transition allows multiple active regions to be stacked vertically, significantly improving productivity while managing fabrication complexity through established semiconductor processing techniques.

The fabrication process is divided into distinct sequential steps: forming isolation structures, creating trenches, depositing semiconductor layers, patterning fins, and forming gate structures. Each step is independently optimized and can be performed using standard semiconductor manufacturing equipment. This segmentation allows complex 3D structures to be built from simpler intermediate stages, making the overall process manageable despite increased device density requirements.

Isolation structures are formed prior to trench etching to define active regions before any complex 3D structures are created. This preliminary step establishes precise boundaries that guide subsequent fabrication steps. By pre-defining where devices will be formed, the patent reduces the precision burden on later patterning steps, as the isolation structures serve as reference features for alignment and dimensional control throughout the fabrication process.

The patent employs nested structures where gate structures wrap around fin structures, which themselves are nested within isolation structures. This nested arrangement allows precise control of channel dimensions through self-aligned processes. The gate structure conformally coats the fin structure, ensuring uniform thickness and precise channel width control without requiring additional lithography alignment steps, thereby enhancing reliability while managing manufacturing precision requirements.

The patent extracts and removes sacrificial materials (such as mandrel structures or temporary fillers) from between the fin structures after the fins are formed. This extraction creates precise gaps and isolation regions that prevent electrical leakage between adjacent devices. By removing these sacrificial elements, the patent achieves clean separation between high-density device regions, reducing parasitic capacitance and leakage current while maintaining the high device density enabled by the vertical fin structures.

Isolation structures serve as intermediary elements between adjacent active device regions. These structures, formed prior to fin creation, act as electrical and physical barriers that prevent unwanted interactions between neighboring devices. The isolation structures mediate the density-performance tradeoff by providing necessary electrical separation while allowing the vertical fin structures to pack closely together, thereby reducing leakage current and parasitic capacitance without sacrificing device density.