Method of making GaAs MOSFET with low source resistance yet having satisfactory leakage current by ion-implantation

Claim 1

A method of making a field effect transistor comprising the steps of: forming a gate electrode on a surface of a first semiconductor region located on a semi-insulating surface; forming a thin film on said first semiconductor region, and on top and side surface of said gate electrode; selectively exposing said surface of said first semiconductor region by selectively removing said thin film disposed away from said side surfaces of said gate electrode at a fixed distance; ion-implanting an impurity of one conductivity type through said exposed surface of said first semiconductor region and through the unremoved thin film, thereby forming: (a) a pair of second semiconductor regions of said one conductivity type deeper than said first semiconductor region at a portion beneath said exposed surface of said first semiconductor region; and (b) a pair of third semiconductor regions of said one conductivity type thinner than said first semiconductor region at portions beneath said thin film except for the portion of said first semiconductor surface occupied by said gate electrode and said thin film formed on said side surfaces of said gate electrode; and forming a source electrode and drain electrode on said surface of said second semiconductor regions, respectively.

Claim 2

A method of making a field effect transistor comprising the steps of: forming a gate electrode on a surface of a first semiconductor region located on a semi-insulating surface; forming a thin film on said first semiconductor region, and on top and side surface of said gate electrode; selectively exposing said surface of said first semiconductor region by selectively removing said thin film disposed away from said side surfaces of said gate electrode at a fixed distance; ion-implanting an impurity of one conductivity type through said exposed surface of said first semiconductor region and through the unremoved thin film, thereby forming: (a) a pair of second semiconductor regions of said one conductivity type deeper than said first semiconductor region at a portion beneath said exposed surface of said first semiconductor region; and (b) a pair of third semiconductor regions of said one conductivity type thinner than said first semiconductor region at portions beneath said thin film except for the portion of said first semiconductor surface occupied by said gate electrode and said thin film formed on said side surfaces of said gate electrode; and forming a source electrode and drain electrode on said surface of said second semiconductor regions, respectively.

Claim 9

A method of making a field effect transistor comprising the steps of: forming a dummy gate on a surface of a first semiconductor region located on a semi-insulating substrate; forming a thin film on said first semiconductor region, and on top and side surfaces of said dummy gate; selectively exposing said surface of said first semiconductor region by selectively removing said thin film disposed away from said side surfaces of said dummy gate at a fixed distannce; ion-implanting impurity of one conductivity type through said exposed surface of said first semiconductor region and through the unremoved thin film, thereby forming: (a) a pair of second semiconductor regions of said one conductivity type deeper than said first semiconductor region at a portion beneath said exposed surface of said first semiconductor region; and (b) a pair of third semiconductor regions of said one conductivity type thinner than said first semiconductor region at portions beneath said thin film except for the portion of said first semiconductor surface occupied by said dummy gate and said thin film formed on said side surfaces of said dummy gate; removing siad thin film; forming a thin layer on said first, second and third removing said dummy gate to expose said surface of said first semiconductor region; forming a gate electrode on said exposed surface of said first semiconductor region; removing said thin layer; and forming a source electrode and a drain electrode on said surface of said second semiconductor regions, respectively.

Claim 10

A method of making a field effect transistor comprising the steps of: forming a dummy gate on a surface of a first semiconductor region located on a semi-insulating substrate; forming a thin film on said first semiconductor region, and on top and side surfaces of said dummy gate; selectively exposing said surface of said first semiconductor region by selectively removing said thin film disposed away from said side surfaces of said dummy gate at a fixed distannce; ion-implanting impurity of one conductivity type through said exposed surface of said first semiconductor region and through the unremoved thin film, thereby forming: (a) a pair of second semiconductor regions of said one conductivity type deeper than said first semiconductor region at a portion beneath said exposed surface of said first semiconductor region; and (b) a pair of third semiconductor regions of said one conductivity type thinner than said first semiconductor region at portions beneath said thin film except for the portion of said first semiconductor surface occupied by said dummy gate and said thin film formed on said side surfaces of said dummy gate; removing siad thin film; forming a thin layer on said first, second and third removing said dummy gate to expose said surface of said first semiconductor region; forming a gate electrode on said exposed surface of said first semiconductor region; removing said thin layer; and forming a source electrode and a drain electrode on said surface of said second semiconductor regions, respectively.

Claim 19

A method of making a GaAs Schottky gate field effect transistor comprising the steps of: forming a Schottky gate electrode on a surface of a first GaAs semiconductor region located on a semi-insulating GaAs substrate; forming a thin film on said first GaAs semiconductor region, and on top and side surfaces of said Schottky gate electrode; selectively exposing said surface of said first GaAs semiconductor region by selectively removing said thin film disposed away from said side surfaces of said Schottky gate electrode at a fixed distance; ion-implanting impurity of one conductivity type through said exposed surface of said first GaAs semiconductor region and through the unremoved thin film, thereby forming: (a) a pair of second GaAs semiconductor regions of said one conductivity type deeper than and having a higher impurity concentration than said first GaAs semiconductor region and at a portion beneath said exposed surface of said first GaAs semiconductor region; (b) a pair of third GaAs semiconductor regions of said one conductivity type thinner than and having a higher impurity concentration than said first GaAs semiconductor region and at portions beneath said thin film except for the portion of said first GaAs semiconductor surface occupied by said Schottky gate electrode and said thin film formed on said side surfaces of said Schottky gate electrode; and forming a source electrode and a drain electrode on said surface of sad second GaAs semiconductor regions, respectively.

Claim 20

A method of making a GaAs Schottky gate field effect transistor comprising the steps of: forming a Schottky gate electrode on a surface of a first GaAs semiconductor region located on a semi-insulating GaAs substrate; forming a thin film on said first GaAs semiconductor region, and on top and side surfaces of said Schottky gate electrode; selectively exposing said surface of said first GaAs semiconductor region by selectively removing said thin film disposed away from said side surfaces of said Schottky gate electrode at a fixed distance; ion-implanting impurity of one conductivity type through said exposed surface of said first GaAs semiconductor region and through the unremoved thin film, thereby forming: (a) a pair of second GaAs semiconductor regions of said one conductivity type deeper than and having a higher impurity concentration than said first GaAs semiconductor region and at a portion beneath said exposed surface of said first GaAs semiconductor region; (b) a pair of third GaAs semiconductor regions of said one conductivity type thinner than and having a higher impurity concentration than said first GaAs semiconductor region and at portions beneath said thin film except for the portion of said first GaAs semiconductor surface occupied by said Schottky gate electrode and said thin film formed on said side surfaces of said Schottky gate electrode; and forming a source electrode and a drain electrode on said surface of sad second GaAs semiconductor regions, respectively.