Field effect transistor (FET) and preparation method thereof

The invention discloses a field effect transistor (FET) and a preparation method thereof. The FET comprises a substrate, a graphene channel region and source/drain contact electrodes, wherein the substrate comprises a back gate material and an insulating medium layer; the graphene channel region is formed above the insulating medium; the source/drain contact electrodes are formed above the insulating medium layer; and the source/drain contact electrodes are respectively in contact with the graphene channel region on the two sides of the graphene channel region. Because the graphene material has huge carrier mobility, the speed of the FET utilizing the graphene as the channel region material can be greatly improved.