Gate structure of field effect transistor with footing

A method, comprising:

• forming a semiconductor structure including a fin protruding from a substrate;
• forming a sacrificial gate electrode layer over the semiconductor structure;
• etching the sacrificial gate electrode layer for forming a sacrificial gate electrode;
• removing the sacrificial gate electrode;
• and
• forming a gate electrode including a central region and footing regions to replace the sacrificial gate electrode, the central region including a gate dielectric, a work function metal layer and a fill metal;
• and
• wherein the gate dielectric and the work function metal layer extend to the footing regions of the gate electrode, and the fill metal is free from extending to the footing regions of the gate electrode.

A method, comprising:

• forming a semiconductor structure including a fin protruding from a substrate;
• forming a sacrificial gate electrode layer over the semiconductor structure;
• etching a first portion of the sacrificial gate electrode layer under a first pressure;
• etching a second portion of the sacrificial gate electrode layer lower the first portion under a second pressure different from the first pressure for forming a central region and footing regions of a sacrificial gate electrode, wherein the footing regions are along where the central region is adjacent to the fin.