A constant distance can be maintained between source/drain regions without providing a gate side wall by forming a gate electrode including an eaves structure, and a uniform dopant concentration is kept within a semiconductor by ion implantation. As a result, a FinFET excellent in element properties and operation properties can be obtained. A field effect transistor, wherein a gate structure body is a protrusion that protrudes toward source and drain regions sides in a channel length direction and has a channel length direction width larger than that of the part adjacent to the insulating film in a gate electrode, and the protrusion includes an eaves structure formed by the protrusion that extends in a gate electrode extending direction on the top surface of the semiconductor layer.