High-speed, low-power-dissipation integrated circuits

Claim 1

A method of making a semiconductor device of the type having an integrated circuit comprising a substrate of a first conductivity type and an epitaxial layer on said substrate and divided into islands of a second opposite conductivity type which are laterally bounded by a surrounding region of the first conductivity type, and a bipolar transistor in at least one island, the surrounding region and the islands being formed by adjoining regions which are diffused from adjacent buried layers of the first and second conductivity types, respectively, through the epitaxial layer, which buried layers are provided in the vicinity of the interface between the substrate and the epitaxial layer and comprise conductivity-determining impurities having substantially the same diffusion rates, p-n junctions being formed between the islands and the surrounding region which are substantially at right angles to the surface of the epitaxial layer throughout their length due to the diffusion of said impurities at substantially the same rate, said method comprising the steps of providing a first dopant determining the second opposite conductivity type in the surface of said substrate via a mask having a plurality of apertures to form island-shaped surface layers of the second conductivity type, providing a second dopant determining the first conductivity type in the whole region between said island-shaped surface layers to form a surface layer of the first conductivity type having a higher doping concentration than the substrate, then epitaxially growing a substantially undoped semiconductor layer on the whole surface and diffusing the surface layers of the first and of the second conductivity type through the whole thickness of the epitaxial layer, and forming said bipolar transistor in at least one of said islands of the second conductivity type.

Claim 2

A method of making a semiconductor device of the type having an integrated circuit comprising a substrate of a first conductivity type and an epitaxial layer on said substrate and divided into islands of a second opposite conductivity type which are laterally bounded by a surrounding region of the first conductivity type, and a bipolar transistor in at least one island, the surrounding region and the islands being formed by adjoining regions which are diffused from adjacent buried layers of the first and second conductivity types, respectively, through the epitaxial layer, which buried layers are provided in the vicinity of the interface between the substrate and the epitaxial layer and comprise conductivity-determining impurities having substantially the same diffusion rates, p-n junctions being formed between the islands and the surrounding region which are substantially at right angles to the surface of the epitaxial layer throughout their length due to the diffusion of said impurities at substantially the same rate, said method comprising the steps of providing a first dopant determining the second opposite conductivity type in the surface of said substrate via a mask having a plurality of apertures to form island-shaped surface layers of the second conductivity type, providing a second dopant determining the first conductivity type in the whole region between said island-shaped surface layers to form a surface layer of the first conductivity type having a higher doping concentration than the substrate, then epitaxially growing a substantially undoped semiconductor layer on the whole surface and diffusing the surface layers of the first and of the second conductivity type through the whole thickness of the epitaxial layer, and forming said bipolar transistor in at least one of said islands of the second conductivity type.