Image Number 2 for United States Patent #4982262.
An area saving dielectrically isolated semiconductor structure is disclosed which allows for the merger of a plurality of active devices, which share a common terminal, in a single dielectrically isolated (DI) island, or tub. In particular, an isolation groove is formed in the bottom of the DI tub and extends upwards toward the top surface of the semiconductor structure. The common diffusion region associated with the common terminal is located in the DI tub directly over the isolation groove. The isolation groove and common diffusion region thus separate the single DI tub into isolated sections, where a separate active device can be formed in each section. Isolation is achieved through the interaction of the groove with the common diffusion region to "pinch off" the conductive channel between devices in the DI tub. In a preferred embodiment, an inverted V-shaped isolation groove is utilized so as not to complicate the fabrication process. In order to merge a large plurality of devices in a single DI tub, a plurality of isolation grooves may be utilized to divide the single DI tub into a number of separate isolated sections.