GATE-DIFFUSION ISOLATION FOR JFET DEPLETION-MODE BUCKET BRIGADE CIRCUIT

Undesired coupling of JFET bucket-brigade stages through the epitaxial layer in a monolithic integrated bucket-brigade circuit is prevented by isolation diffusion regions formed in the epitaxial layer along the two sides of a row of bucket-brigade stages. The isolation diffusion regions are slightly spaced from the JFET gate diffused regions and reverse-biased so that depletion regions extend down to the substrate. The close spacing of the gate and isolation diffusion regions results in the gate and isolation depletion regions joining upon application of voltage to the gate to pinch off the transistor. The storage capacitors of the bucket-brigade stages are MOS devices formed by metal layers overlapping the JFET drain electrode regions diffused in the epitaxial layer with the capacitor dielectric being a dielectric layer therebetween.