Junction-type field-effect transistor and its manufacture

DETAILED DESCRIPTION What is claimed is: 1.
A junction field effect transistor which comprises a semiconductor body having a major surface, a surface-adjacent semiconductor layer of a first conductivity type, spaced-apart and parallel source and drain zones of a second conductivity type opposite to that of the first in said semiconductor layer, a surface-adjacent layer-shaped gate region of said first conductivity type, and a layer-shaped channel region of said second conductivity type beneath said gate region, said gate region and said channel region both extending laterally to said source and drain zones, said gate region forming part of a first semiconductor zone of said first conductivity type and said channel region forming part of a second semiconductor zone of said second conductivity type, said first and second semiconductor zones being formed by ion implantation through the same mask, said first and second semiconductor zones extending longitudinally beyond said parallel source and drain zones in a direction parallel to said source and drain zones and being substantially longitudinally coextensive, and said gate region being connected to said semiconductor layer by at least one highly doped connection zone of said first conductivity type adjoining at least said first semiconductor zone of the first conductivity type.
2.
A junction field effect transistor as claimed in claim 1 characterized in that said connection zone has a thickness substantially equal to the thickness of said gate region.
3.
A junction field effect transistor as claimed in claim 1 characterized in that said connection zone has a thickness at least equal to the total thickness of said gate region and said channel region.




Description:
BACKGROUND OF THE INVENTION 1.
Field of the Invention The invention relates to junction-type field-effect transistors, especially but not exclusively very sensitive field-effect transistors which operate on low supply voltages with low threshold voltages and which may be used in particular as input elements for low noise level operational amplifiers, for example the amplifiers installed in sensors for medical uses