Gate structure for semiconductor device

A fin field effect transistor (finFET), comprising:

• a fin structure comprising a top surface, wherein the fin structure extends in a horizontal direction;
• a dielectric layer on the fin structure;
• and
• a gate electrode on the dielectric layer, comprising:
• a first portion, above the top surface of the fin structure, comprising a first dimension along the horizontal direction;
• and
• a second portion, below the top surface of the fin structure, comprising a second dimension along the horizontal direction, wherein the first dimension is less than the second dimension.

A fin field effect transistor (finFET), comprising:

• a substrate;
• a fin structure, on the substrate, comprising a top surface;
• a dielectric layer on the fin structure;
• and
• a gate electrode, on the dielectric layer, comprising a first gate length, a second gate length, and a third gate length, wherein:
• the first gate length at a top portion of the gate electrode is less than the second gate length at a middle portion of the gate electrode;
• and
• the third gate length at a bottom portion of the gate electrode and below the top surface of the fin structure is greater than the second gate length.