An embodiment of the present invention discloses a method for manufacturing a FinFET, when a fin is formed, a dummy gate across the fin is formed on the fin, a source/drain opening is formed in both the cover layer and the first dielectric layer at both sides of the dummy gate, the source/drain opening is at both sides of the fin covered by the dummy gate and is an opening region surrounded by the cover layer and the first dielectric layer around it. In the formation of a source/drain region in the source/drain opening, stress is generated due to lattice mismatching, and applied to the channel due to the limitation by the source/drain opening in the first dielectric layer, thereby increasing the carrier mobility of the device, and improving the performance of the device.