Insulated gate field effect transistor

Claim 1

1 c A semiconductor device having a.semiconductor body comprising a surface-adjoining first region of a first conductivity type in which an insulated gate field effect transistor is provided, having highly doped source and drain zones of the second opposite conductivity type, a surface zone of the second conductivity type adjoining the drain zone and having a lower doping concentration than the drain zone, said surface zone extending in the direction of the source zone, a channel region of the first conductivity type present between said surface zone and the source zone, and a gate electrode present above the channel region and separated from the channel region an'electrically insulating layer, a field plate being provided between the source and drain zones and extending in the direction of the drain zone to above the said surface zone but not to above the drain zone and being insulated from the semiconductor surface, said field plate comprising a connection conductor, characterized in that the first region is an epitaxial layer forming with a substrate of the second conductivity type a p-n. junction which in operation is reverse biased, that a buried layer of the first conductivity type having a higher doping concentration than the epitaxial layer is provided between said epitaxial layer and the substrate and below at least the channel region and a part of the surface zone, said buried layer not extending below the drain zone, and that the field plate extends above the surface zone on insulating layer parts of a thickness increasing in the direction of the drain zone, as a result of which in the direction of the drain zone successive parts of the surface zone are successively pinched off when the drain voltage increases.