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US 5,688,701 AGranted
Method of making semiconductor device having a plurality of impurity layers
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsMaiko Kobayashi, Takashi Kuroi
Life of this patent
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Abstract
A semiconductor device in which ability for isolating elements from each other can be improved and increase in substrate constant and junction capacitance can be suppressed, is disclosed. An impurity layer for improving the ability for isolating elements is positioned only immediately below an isolating insulating film. An impurity layer for adjusting substrate constant and junction capacitance is formed through independent steps from the impurity layer for improving the isolating ability.
Claims8
A method of manufacturing a semiconductor device, comprising the steps of:
- forming an isolating insulating film for isolating elements from each other on a main surface of a semiconductor substrate;
- forming a mask layer for preventing passage of an impurity, on a main surface of an element forming region surrounded by said isolating insulating film;
- forming a first impurity layer only immediately below said isolating insulating film, by ion-implanting an impurity through said isolating insulating film on the main surface of semiconductor substrate having said mask layer;
- forming a second impurity layer at a position deeper than said first impurity layer, by ion-implanting an impurity, after removal of said mask layer, through the main surface of said element forming region and through said isolating insulating film;
- forming a third impurity layer at a position deeper than said second impurity layer by ion-implanting an impurity through the main surface of said element forming region and through said isolating insulating film;
- and
- forming a fourth impurity layer at a position near the main surface of said element forming region but not below said isolating insulating film.
4 more elements
Dependencies are inferred from the claim text.