A method of fabricating a semiconductor device, including the following steps. A plurality of fin structures are formed on a substrate. There is a trench between the fin structures. At least two times of circulating processes are performed. The circulating processes include: a deposition process and an etching process. The deposition process is performed to fill a first conductor material layer in the trench. The first conductor material layer covers top parts and sidewalls of the fin structures. The etching process is performed to remove a part of the first conductor material layer.