The present application discloses a MOSFET and a method for manufacturing the same. The MOSFET comprises an SOI wafer, which comprises a bottom semiconductor substrate, a first buried insulating layer on the bottom semiconductor substrate, and a first semiconductor layer on the first buried insulating layer; a source region and a drain region which are formed in a second semiconductor layer over the SOI wafer, wherein there is a second buried insulating layer between the second semiconductor layer and the SOI wafer; a channel region, which is formed in the second semiconductor layer and located between the source region and the drain regions; and a gate stack, which comprises a gate dielectric layer on the second semiconductor layer and a gate conductor on the gate dielectric layer, wherein the MOSFET further comprises a backgate formed in a portion of the first semiconductor substrate below the channel region, the backgate having a non-uniform doping profile, and the second buried insulating layer serving as a gate dielectric layer of the backgate. The MOSFET has an adjustable threshold voltage by changing the polarity of dopants and/or the doping profile in the backgate. Leakage in the semiconductor device can be reduced.