The invention discloses a Fin FET and a manufacturing method thereof. The Fin FET comprises a semiconductor substrate, a first doping type punchthrough preventing layer located on the semiconductor substrate, a semiconductor fin located on the punchthrough preventing layer, a grid stacking layer connected with the semiconductor fin, a second doping type source region, a second doping type drain region, a source contact and a drain contact, wherein the grid stacking layer comprises a grid electrode conductor and a grid electrode dielectric medium, the grid electrode dielectric medium is located between the grid electrode conductor and the semiconductor fin, the second doping type source region and the second doping type drain region are formed in the part, adjacent to the grid stacking layer, of the semiconductor fin, the second doping type is reverse to the first doping type, the source region and the drain region respectively comprise a top part and a side face, the source contact and the drain contact are in contact with the source region and the drain region respectively, the source contact is in contact with the surface of the top of the source region and is separated from at least one part of the side face of the source region, and the drain contact is in contact with the surface of the top of the drain region and is separated from at least one part of the side face of the drain region. According to the Fin FET, short circuit between the source/drain region and the punchthrough preventing layer is avoided, and the reliability of the Fin FET is improved.