Semiconductor device and fabricating method thereof

A method for fabricating a semiconductor device, comprising:

• providing a substrate;
• forming a first and second source/drain (S/D) regions on the substrate;
• and
• forming a gate stack over the substrate to overlay a channel region between the first and second S/D regions, comprising:
• forming a gate dielectric layer over the substrate;
• and
• forming a metal alloy on the gate dielectric layer to be a filling layer in the gate stack;
• wherein the metal alloy has a first corrosion resistance corresponding to an etchant designed for removing a carbon-containing polymer, and forming the metal alloy includes sputtering an Al—Si—Cu target.

A method for fabricating a semiconductor device, comprising:

• providing a substrate;
• forming a first and second source/drain (S/D) regions on the substrate;
• and
• forming a gate stack over the substrate to overlay a channel region between the first and second S/D regions, comprising:
• forming a gate dielectric layer over the substrate;
• forming a metal alloy on the gate dielectric layer to be a filling layer in the gate stack;
• forming a work function layer over the gate dielectric layer;
• forming a blocking layer over the work function layer;
• and
• forming a wetting layer over the blocking layer;
• wherein the metal alloy is disposed over the wetting layer, and the metal alloy has a first corrosion resistance corresponding to an etchant designed for removing a carbon-containing polymer.