A method of fabrication of a metal oxide semiconductor field effect transistor is disclosed. At first, a substrate on which a gate structure is formed is provided. Afterward, a portion of the substrate is removed to form a first recess in the substrate at both ends of the gate structure. Additionally, a source/drain extension layer is deposited in the first recess and a plurality of spacers are formed at both ends of the gate structure. Subsequently, a portion of the source/drain extension and the substrate are removed to form a second recess in the source/drain extension and a portion of the substrate outside of the spacer. In addition, a source/drain layer is deposited in the second recess. Because the source/drain extension and the source/drain layer have specific materials and structures, short channel effect is improved and the efficiency of the metal oxide semiconductor field effect transistor is improved.