FinFET formation process and structure

A FinFET and methods for forming a FinFET are disclosed. In a method, first trenches are formed in a substrate. First isolation regions are then formed in the first trenches. An epitaxial region is epitaxially grown between the first isolation regions. A second trench is formed by etching in the epitaxial region, forming a plurality of fins. A second isolation region is formed in the second trench. A structure includes a substrate, a first fin on the substrate, a gate dielectric over the first fin, and a gate electrode over the gate dielectric. The first fin comprises an epitaxial layer having a stacking fault defect density less than 1*104 cm .