Fin field-effect transistor device and method of forming the same

A semiconductor device comprising:

• a substrate;
• a fin protruding above the substrate;
• isolation regions on opposing sides of the fin;
• a gate structure over the fin, wherein the gate structure comprises a gate dielectric layer and a gate electrode over the gate dielectric layer;
• gate spacers along opposing sidewalls of the gate structure;
• and
• a gate fill material around the gate structure, wherein the gate fill material is disposed laterally between the gate spacers and the gate structure, and is disposed vertically between the gate structure and the isolation regions.

A semiconductor device comprising:

• a fin that protrudes above a substrate;
• isolation regions on opposite sides of the fin;
• a gate structure over the fin, wherein the gate structure comprises a gate dielectric layer and a gate electrode over the gate dielectric layer;
• gate spacers along opposite sidewalls of the gate structure, wherein a lower portion of the gate structure extends into the isolation regions, wherein the lower portion of the gate structure tapers off as the gate structure extend toward the isolation regions;
• and
• a gate fill material along sidewalls of the lower portion of the gate structure, wherein the gate fill material is between the gate spacers and the gate structure, wherein a width of the gate fill material along the sidewalls of the lower portion of the gate structure increases as the gate fill material extends toward the isolation regions.