Self-aligned trench contacts via replacement gate mandrels

The patent applies preliminary action by forming the trench contact pattern before the gate pattern through a sequence of preparatory steps: forming mandrels, depositing first and second spacer layers, and performing selective etching to create the trench contact opening. This preliminary structuring establishes self-alignment features that guide subsequent gate formation, ensuring accurate alignment without requiring complex alignment procedures at later stages.

The patent implements self-service through self-aligned processes where the trench contact structure automatically defines the gate position. The mandrel and spacer layers create physical references that guide material deposition and etching steps, allowing the structure to self-align without external alignment tools or complex photolithography steps. The trench contact opening position is determined by the mandrel-spacer geometry rather than separate alignment operations.

The patent applies segmentation by dividing the alignment problem into distinct functional layers: mandrels provide the primary alignment reference, the first spacer layer defines lateral offsets, and the second spacer layer refines the trench contact position. Each layer performs a specific alignment function, breaking down the complex alignment task into manageable segments that can be formed using standard deposition and etching processes rather than requiring a single complex self-aligned step.

The patent uses parameter changes by varying the thicknesses and materials of the mandrel and spacer layers to control the final trench contact dimensions and position. By adjusting spacer layer thickness parameters, the process achieves precise alignment control while using conventional deposition techniques. The etch selectivity parameters between different layers are optimized to enable selective removal of materials without affecting adjacent structures, simplifying the overall manufacturing process.