GaAs MESFET having LDD and non-uniform P-well doping profiles

Abstract

A MESFET has a conduction channel provided with a first doping profile in a first portion which extends between the source and the gate, and a second doping profile in a second portion which extends between the gate and the drain. A background p-type region is provided beneath the first portion, but not necessarily behind the second portion.

What is claimed is:  
     
         1 . A metal-semiconductor field effect transistor (MESFET) comprising: 
 a substrate;    a source region formed in the substrate and having a source electrode;    a drain region formed in the substrate and having a drain electrode;    a conduction channel formed in the substrate between the source region and the drain region; and    a gate electrode positioned between the source region and the drain region, the gate electrode also being above the conduction channel; wherein    the conduction channel has a first doping profile in a first portion thereof between the source region and the gate electrode, and a second doping profile in a second portion thereof between the gate electrode and the drain region.    
     
     
         2 . The MESFET according to  claim 1 , wherein: 
 a p-type background region is implanted in the substrate beneath the first portion, but not beneath the second portion.    
     
     
         3 . The MESFET according to  claim 2 , wherein the first portion is doped with n-type ions.  
     
     
         4 . The MESFET according to  claim 3 , wherein the first portion is more heavily doped than the second portion.  
     
     
         5 . The MESFET according to  claim 1 , wherein: 
 the p-type background region merges with the first portion.    
     
     
         6 . The MESFET according to  claim 1 , wherein the first portion is more heavily doped than the second portion.  
     
     
         7 . The MESFET according to  claim 1 , wherein the substrate is formed from GaAs.