FinFET Metal Gate WFM Tuning for Threshold Voltage Control

The patent applies local quality by using different work function adjustment layer configurations for different transistor types. Specifically, first-type-channel transistors receive a first work function adjustment layer while second-type-channel transistors receive a second work function adjustment layer with different material composition or thickness. This localized differentiation enables precise threshold voltage control for each transistor type without unnecessarily complicating the entire device structure, as each region receives only the specific treatment it requires.

The patent applies preliminary action by forming a protective layer on the gate structure before performing etching operations to create self-aligned contact structures. This protective layer is deposited in advance to shield the gate from etching damage, and is subsequently removed after the etching is complete. This preliminary protective measure enables the necessary multiple etching steps to achieve high precision self-aligned contact structures while minimizing harmful etching damage to the gate, as the gate is protected during the etching process.