A method for manufacturing a multigate device is provided, comprising: providing a semiconductor substrate; etching the semiconductor substrate to form a protruding fin; etching the semiconductor substrate at the bottom of the fin so as to form a gap between the fin and the semiconductor substrate; forming a dielectric layer which covers the semiconductor substrate and the fin and fills the gap; and etching the dielectric layer so as to expose the top and a portion of sidewalls of the fin. The present invention can realize isolation between fins with a simple process, which costs relatively low and is suitable for massive industrial application.