Production method for ion-implanted MESFET having self-aligned lightly doped drain structure and T-type gate

Claim 1

Production method for ion-implanted MESFET (Metal Semiconductor Field Effect Transistor) having self-aligned LDD structure and T-gate, said method comprising the steps of: forming a channel region of a first conductivity type at a part of a semi-insulated compound semiconductor substrate; forming source and drain regions at both ends of said channel region having an impurity of the same conductivity type as said channel region at a higher doping concentration than at a center portion of said channel region; forming a caps layer on a first part of said channel region, and forming a reverse mesa having different separation between said reverse mesa and, respectively, said source region and drain region on said channel region by wet-etching an exposed portion of said semiconductor substrate by using the caps layer as a mask, said reverse mesa having a bottom width smaller than a top width; forming a source and a drain having a lower doping concentration of the same conductivity type than said source and drain regions between said channel region and respective said source and drain regions by using said caps layer as the mask; removing said caps layer, and forming a protective film so as to expose an upper surface of the reverse mesa on a top part of said semiconductor substrate; removing said protective film to expose said source and drain regions and forming source and drain electrodes; and removing said reverse mesa, and forming a T-shape gate electrode at said first part of said channel region.