Abstract of the Disclosure

Disclosed are monolithic circuits of the type having matched pairs of complementary transistors formed within respective pockets of an epitaxial layer that extends over one surface of a substrate. Below the emitter and base regions of each transistor is a diffused region of conductivity type opposite to the conductivity of the substrate, and formed within the diffused region below the NPN transistor is a buried region of conductivity type the same as the conductivity type of the substrate for providing a low resistivity path for collector current. In other pockets of the epitaxial layer, there may be formed sub-epitaxial resistors, surface resistors, n-channel field effect transistors and p-channel field effect transistors.

• Figures 1a and 1b, collectively, show a single substrate after the first p-type diffusion upon which six different circuit devices are to be fabricated concurrently in accordance with the process of this invention.
• Figures 2a and 2b, collectively, show the substrate of Figures 1a and 1b after the preepitaxial n-type diffusion step of the process.

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