Patent ID: 7956437

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 first floor isolation region of a second conductivity type opposite to the first conductivity type submerged in the substrate; and an annular dielectric-filled trench extending downward from a surface of the substrate at least to the first floor isolation region; wherein the first floor isolation region and the dielectric-filled trench together enclose a first isolated pocket of the substrate the structure further comprising: a second floor isolation region of the second conductivity type spaced apart laterally from the first floor isolation region; a second annular dielectric-filled trench extending downward from the surface of the substrate at least to the second floor isolation region, wherein the second floor isolation region and the second annular dielectric-filled trench together enclose a second isolated pocket of the substrate; and a third dielectric-filled trench extending downward from the surface of the substrate, the third dielectric-filled trench extending between the first and second floor isolation regions to a level below the first and second floor isolation regions.