Field effect transistor including multiple aspect ratio trapping structures

The present disclosure relates to a field-effect transistor and a method of fabricating the same. A field-effect transistor includes a semiconductor substrate including a first semiconductor material having a first lattice constant, and a fin structure on the semiconductor substrate. The fin structure includes a second semiconductor material having a second lattice constant that is different from the first lattice constant. The fin structure further includes a lower portion that is elongated in a first direction, a plurality of upper portions protruding from the lower portion and elongated in a second direction that is different from the first direction, and a gate structure crossing the plurality of upper portions.