Differential metal gate etching process

A method for performing a differential metal gate etching process, comprising:

• disposing a substrate in a plasma processing system, said substrate having a differential metal gate structure including a metal gate layer overlying a high dielectric constant (high-k) dielectric layer, wherein said metal gate layer comprises a first thickness for a first region on said substrate and a second thickness for a second region on said substrate, said second thickness being greater than said first thickness;
• and
• performing a differential metal gate etching process for pattern etching said metal gate layer through said first thickness at said first region and said second thickness at said second region, wherein said differential metal gate etching process comprises at least one etch step that includes forming plasma using a halogen-containing gas and at least one etch step that includes forming plasma using an additive gas having C, H, and F as atomic constituents.