Semiconductor device

A semiconductor device, comprising:

• a substrate;
• a first transistor disposed on the substrate, and comprising a first gate structure, wherein the first gate structure comprises a first high-k layer, a first work function layer, and a first capping layer sequentially disposed on the substrate;
• and
• a second transistor disposed on the substrate, and comprising a second gate structure, wherein the second gate structure comprises a second high-k layer, a second work function layer, and a second capping layer sequentially disposed on the substrate,
• wherein a material of the second work function layer comprises Ta element and Al element,
• wherein the material of the first capping layer and the second capping layer comprise a material having higher resistant to oxygen or fluorine than materials of the second work function layer.

A semiconductor device, comprising:

• a substrate;
• a plurality of semiconductor nanosheets disposed over the substrate;
• and
• a gate stack wrapping each of the plurality of semiconductor nanosheets, wherein the gate stack comprises:
• a gate dielectric layer wrapping each of the plurality of semiconductor nanosheets;
• a work function layer surrounding the gate dielectric layer;
• a gate fill material surrounding the work function layer;
• and
• a barrier layer between the work function layer and the gate fill material, wherein the barrier layer is located in an inner sheet region between two adjacent semiconductor nanosheets and in an outer sheet region other than the inner sheet region.