FinFET Gate And Contact Layout For SiGe Strain Retention

The patent removes the isolation structure from between abutted circuit cells, extracting the source of strain loss. By eliminating the isolation structure that caused strain relaxation in SiGe fins, the invention maintains strain in the fin regions while still achieving adequate isolation through alternative means such as dielectric layers formed after fin patterning.

The patent performs fin patterning and strain layer formation before forming dielectric isolation layers. By establishing the fin structures and strain layers first, the invention ensures that strain is maintained in the SiGe fins before any isolation structures are introduced, preventing strain loss that would occur with traditional isolation-first approaches.

The patent combines the isolation function with the gate dielectric layer formation process. Instead of using separate gate cut processes to isolate circuit cells, the invention forms a continuous gate dielectric layer that provides isolation between abutted cells while maintaining gate functionality, thereby merging isolation and gate formation into a single integrated process.

The gate dielectric layer serves multiple functions simultaneously: it acts as the gate insulator for transistor operation and provides isolation between abutted circuit cells. This multi-functional approach eliminates the need for dedicated isolation structures or gate cut processes, reducing fabrication complexity while maintaining both gate functionality and cell isolation.

The patent employs multi-patterning techniques where patterns are formed in nested stages. First, mandrel structures are formed and patterned; then spacer layers are deposited conformally on the mandrels; finally, the mandrels are removed and the spacers form the final pattern. This nested approach enables pitch reduction by effectively doubling or quadrupling the pattern density while using standard lithography tools.

The patent uses spacer layers as intermediary structures to transfer patterns from mandrels to final features. The spacers act as a mediating element that allows pattern multiplication without requiring direct lithographic patterning at the final pitch, enabling precise pattern formation through self-aligned deposition and etching processes.