The present invention relates to a SON (Silicon-On-Nothing) MOSFET having a beam structure and an inverter using thereof and the method for fabricating thereof to increase the efficiency and performance of a MOSFET. A method for fabricating the SON MOSFET according to the present invention comprises the steps of (a) patterning a passivation layer on a substrate, (b) doping boron on the substrate, (c) removing the patterned passivation layer, (d) forming the beam structure on the substrate by anisotropical etching on the region not doped with boron of the substrate, (e) depositing an insulating material on the substrate having the beam structure, and (f) deposing an electrode material on the disposed insulating material.