Field-effect transistor - has two source regions of different impurity concentration but higher than channel or drain

A multichannel field-effect transistor (FET) with a controlled junction has first source regions with a high impurity concn. A second source region extends downwards from one of the first source regions and is doped less than the first source region but more than the substrate. The second source region lies within a window of the insulating layer and extends below it into a channel. A FET of this type has excellent triode properties without reduction of the breakdown voltage between gate and source region. The transistor has good ohmic properties in the source contact.