In a recessed structure MESFET, an active layer (n-type layer) 2 is provided on a high resistance GaAs substrate 1, a pair of contact layers (n.sup.+ -type layers) 31, 32 is provided on the active layer 2, a source electrode 6 is provided on one contact layer 31, a drain electrode 7 is provided on the other contact layer 32 and a gate electrode 5 is provided on the active layer 2 to achieve a recessed structure. A semiconductor layer 4 having a lower impurity density than that of the contact layer 31, 32 is formed at the recess edge portion at at least drain side to alleviate the concentration of the electric field and current there to suppress the generation of electron-holes pairs by collision ionization to reduce the damage to the crystal lattice by non-luminescence recombination of the electron-holes thus preventing the degradation of the FET characteristics.