The present disclosure provides a FinFET. The FinFET includes a silicon-on-insulator (SOI) with an insulator; a plurality of fin structures on the insulator; an isolation on the insulator, and between two adjacent fin structures in the plurality of fin structures; and an oxide layer between each of the plurality of fin structures and the insulator, wherein the insulator comprises silicon germanium oxide. A method for manufacturing the FinFET includes forming a plurality of fin structures on a layer having a larger lattice constant than that of the fin structure by a patterning operation; oxidizing the fin structure and the layer to transform the layer into a first oxide layer; filling insulating material between adjacent fin structures; and etching the insulating material to expose a top surface and at least a portion of a sidewall of the fin structure.