Semiconductor structure and method of forming the same

A method of forming a semiconductor structure, comprising:

• forming a first work function layer on a substrate;
• forming a second work function layer on the first work function layer;
• forming a protective layer on the second work function layer;
• forming a gate stack on the protective layer;
• forming a first liner on a top surface and side surfaces of the gate stack;
• forming a second liner on a top surface and side surfaces of the first liner;
• forming a planarization layer on the second liner;
• performing an etching process, to remove the second work function layer and expose the first work function layer;
• and
• forming a gate plug on the planarization layer and a wire on the protective layer, so that the gate plug is in contact with the first work function layer and the second work function layer, and the wire is in electrical contact with the gate plug and extends through both the first liner and the second liner.