Patent ID: 7825488

Claim:
An isolation structure formed in a semiconductor substrate of a first conductivity type, the substrate not comprising an epitaxial layer, the structure comprising: a floor isolation region of a second conductivity type opposite to the first conductivity type submerged in the substrate; an annular trench extending downward from a surface of the substrate at least to the floor isolation region, walls of the trench being lined with a dielectric material, the trench containing a conductive material, the conductive material in the trench being in electrical contact with the floor isolation region, wherein the floor isolation region and trench together enclose an isolated pocket of the substrate; a second floor isolation region of the second conductivity type spaced apart laterally from the floor isolation region; a second annular trench extending downward from the surface of the substrate at least to the second floor isolation region, walls of the second annular trench being lined with the dielectric material, the second annular trench containing the conductive material, the conductive material in the second annular trench being in electrical contact with the second floor isolation region, wherein the second floor isolation region and second annular trench together enclose a second isolated pocket of the substrate; and a region of the first conductivity type located laterally between the floor isolation region and the second floor isolation region, a doping concentration of the region of the first conductivity type being greater than a doping concentration of the substrate.