Methods for Forming Fin Field-Effect Transistors

A device comprising:

• a first fin and a second fin separated by a first trench in a substrate, the first trench having a first depth;
• a second trench in the substrate adjacent the first fin, the second trench having a second depth, the second depth being the same as the first depth;
• a third trench in the substrate adjacent the second trench, the third trench having a third depth, the third depth being greater than the second depth;
• an isolation material in the first trench, the second trench, and the third trench, wherein a thickness of the isolation material in the third trench is greater than a thickness of the isolation material in the second trench, and wherein the isolation material extends continuously from the second trench to the third trench;
• a gate dielectric over the first fin and over the second fin;
• and
• a gate electrode over the gate dielectric, wherein the gate electrode extends from the second fin horizontally over the isolation material in the second trench and the third trench, and wherein the gate electrode extending horizontally from the second fin over the isolation material in the second trench and the third trench has a uniform thickness.

A device comprising:

• a first fin structure extending from the substrate, the first fin structure comprising two adjacent fins, the two adjacent fins separated by a first distance;
• a substrate depression in the substrate, wherein the substrate depression has a first width in a first dimension and a second width in the first dimension, the first width being greater than the second width, the first width corresponding to a combined width of the two adjacent fins of the first fin structure and the first distance, wherein a first end of the first width corresponds to a first sidewall of the substrate depression, wherein a second end of the first width opposite the first end corresponds to a second sidewall of the substrate depression opposite the first sidewall;
• an isolation structure extending from the first fin structure into the substrate depression, wherein a portion of the first fin structure extends above a top surface of the isolation structure;
• and
• a gate structure over the first fin structure, the gate structure comprising a gate dielectric and a gate electrode over the gate dielectric.