Method of manufacturing schottky gate field transistor by ion implantation method

Claim 1

A method of manufacturing field effect transistors by an ion-implantation technique comprising the steps of: (a) preparing a plurality of compound semiconductor substrates, forming field effect transistors on each of said semiconductor substrates, each of said field effect transistors having an active layer formed by ion-implanting donor ions into said substrate and annealing the same at a temperature of about 800° C., each of said substrates having a source electrode, a drain electrode and a Schottky barrier gate electrode thereon, said source electrode and drain electrode both containing gold and germanium and making ohmic contact with said active layer; (b) measuring a threshold voltage of said field effect transistors and selecting a substrate in which the threshold voltage of the field effect transistor formed thereon has a value deviating negatively from a predetermined designated voltage; and (c) selectively ion-implanting impurity ions, which damage the substrate by causing crytal defects therein, in an amount of less than 1.0 ×10 11 dose/cm 2 into said selected substrate to form an impurity ion profile such as to have a concentration peak thereof at a location in the substrate deeper than that of a concentration peak of donor ions in said active layer.

Claim 2

A method of manufacturing field effect transistors by an ion-implantation technique comprising the steps of: (a) preparing a plurality of compound semiconductor substrates, forming field effect transistors on each of said semiconductor substrates, each of said field effect transistors having an active layer formed by ion-implanting donor ions into said substrate and annealing the same at a temperature of about 800° C., each of said substrates having a source electrode, a drain electrode and a Schottky barrier gate electrode thereon, said source electrode and drain electrode both containing gold and germanium and making ohmic contact with said active layer; (b) measuring a threshold voltage of said field effect transistors and selecting a substrate in which the threshold voltage of the field effect transistor formed thereon has a value deviating negatively from a predetermined designated voltage; and (c) selectively ion-implanting impurity ions, which damage the substrate by causing crytal defects therein, in an amount of less than 1.0 ×10 11 dose/cm 2 into said selected substrate to form an impurity ion profile such as to have a concentration peak thereof at a location in the substrate deeper than that of a concentration peak of donor ions in said active layer.