Abstract: A semiconductor device includes multiple low voltage N-well (LVNW) areas biased at different potentials and isolated from a substrate by a common N+ buried layer (NBL) and at least one high voltage N-well (HVNW) area. The LVNW areas are coupled to the common, subjacent NBL through a common P+ buried layer (PBL). The method for forming the substrate usable in a semiconductor device includes forming the NBL in a designated low voltage area of a negatively biased P-type semiconductor substrate, forming the PBL in a section of the NBL area by implanting P-type impurity ions such as indium into the PBL, and growing a P-type epitaxial layer over the PBL using conditions that cause the P-type impurity ions to diffuse into the P-type epitaxial layer such that the PBL extends into the NBL. Low-voltage P-well areas are also formed in the P-type epitaxial layer and contact the PBL.

Abstract: Method and apparatus for a semiconductor device including high voltage MOS transistors is described. A substrate is provided with a low voltage and a high voltage region separated one from the other. Isolation regions containing an insulator are formed including at least one formed within one of said wells within the high voltage region. The angle of the transition from the active areas to the isolation regions in the high voltage device region is greater than a predetermined angle, in some embodiments it is greater than 40 degrees from vertical. In some embodiments the isolation regions are formed using shallow trench isolation techniques. In alternative embodiments the isolation regions are formed using field oxide formed by local oxidation of silicon techniques.

Abstract: A semiconductor structure includes an isolation ring disposed on a semiconductor substrate, surrounding first and second circuit areas. A buried isolation layer is continuously extended through the first circuit area and the second circuit area, in the semiconductor substrate. The buried isolation layer interfaces with the isolation ring, thereby isolating the first and second circuit areas from a backside bias of the semiconductor substrate. An ion enhanced isolation layer separates the first well in the first circuit area and the second well in the second circuit areas from the isolation ring and the buried isolation layer, thereby preventing punch-through between the wells of the circuit areas and the buried isolation layer.