Patent ID: 6864525

Claim:
A charge pump device having a plurality of transistors for charge transfer connected in series and outputting a boosted voltage from a last stage of the plurality of transistors for charge transfer, comprising: a single crystalline semiconductor substrate of a first conductivity type; a first epitaxial semiconductor layer of a second conductivity type grown on the single crystalline semiconductor substrate; a second epitaxial semiconductor layer of the second conductivity type stacked on the first epitaxial semiconductor layer; a plurality of well regions of the first conductivity type formed in the second epitaxial semiconductor layer and separated from each other; an isolation layer of the first conductivity type formed between the well regions; a first buried layer of the first conductivity type abutting on a bottom of each of the well regions of the first conductivity type; a second buried layer of the second conductivity type abutting on a bottom of the first buried layer of the first conductivity type and electrically isolating each of the well regions of the first conductivity type from the single crystalline semiconductor substrate, wherein each of the transistors for charge transfer is formed in each of the well regions of the first conductivity type; and a diffusion layer of the first conductivity type formed in each of the plurality of well regions, wherein each of the transistors for charge transfer includes a respective drain layer, and wherein the diffusion layer in a particular well region is connected electrically to the drain layer of the transistor in the same well region.