Abstract: A method of fabricating a trimmed fin includes: forming a preliminary fin including silicon and germanium protruding from a substrate, in which the preliminary fin has a first germanium concentration at a top surface of the preliminary fin and a second germanium concentration at a position beneath the top surface of the preliminary fin, and the first germanium concentration is less than the second germanium concentration; oxidizing an exposed surface of the preliminary fin to form a trimmed fin covered by an oxide layer; and removing the oxide layer to obtain the trimmed fin.