Triple well isolated diode and method of making

A semiconductor device comprising:

• a boost converter circuit, wherein the boost converter circuit comprises:
• a triple well isolated diode comprising:
• a substrate having a first conductivity type;
• a buried layer in the substrate, wherein the buried layer has a second conductivity type opposite to the first conductivity type;
• an epi-layer over the substrate and the buried layer, wherein the epi-layer has the first conductivity type;
• a first well in the epi-layer, wherein the first well has the second conductivity type;
• a second well in the epi-layer and surrounding sides of the first well, wherein the second well has the first conductivity type;
• a third well formed in the epi-layer and surrounding sides of the second well, wherein the third well has the second conductivity type;
• and
• a deep well in the epi-layer extending beneath the first well to electrically connect to the second well on opposite sides of the first well, wherein the deep well has the first conductivity type.

A method of making a triple well isolated diode comprising:

• forming a buried layer in a substrate, wherein the buried layer has a second conductivity type and the substrate has a first conductivity type opposite to the second conductivity type;
• forming an epi-layer over the substrate and the buried layer, wherein the epi-layer has the first conductivity type;
• forming a first well in the epi-layer, wherein the first well has the second conductivity type;
• forming a second well in the epi-layer, wherein the second well has the first conductivity type and surrounds the first well;
• forming a third well in the epi-layer, wherein the third well has the second conductivity type and surrounds the second well;
• and
• forming a deep well in the epi-layer, wherein the deep well has the first conductivity type and extends beneath the first well to electrically connect to the second well on both sides of the first well.