Optoelectronic device including photodiode having buried layer with different thicknesses

A device comprising:

• a substrate;
• a first well of a first conductivity type in the substrate, the first well has a side boundary;
• a second well of a second conductivity type in the substrate, the second conductivity type is of an opposite conductivity type to the first conductivity type, the first well is concentric with and laterally surrounded by the second well;
• and
• a buried layer of the second conductivity type in the substrate, the buried layer is below the first well and the second well, the buried layer has a first section and a second section, the first section is concentric with and laterally surrounded by the second section, the second section of the buried layer has a lower dopant concentration than the first section of the buried layer, wherein the first section of the buried layer is aligned vertically below and in direct contact with the first well, and wherein the first section of the buried layer has a side boundary, and the side boundary of the first section of the buried layer is coplanar with the side boundary of the first well.

A method of forming a device, the method comprising:

• forming a first well of a first conductivity type in a substrate, the first well has a side boundary;
• forming a second well of a second conductivity type in the substrate, the second conductivity type is of an opposite conductivity type to the first conductivity type, the first well is formed to be concentric with and laterally surrounded by the second well;
• and
• forming a buried layer of the second conductivity type in the substrate, the buried layer is formed below the first well and the second well, the buried layer has a first section and a second section, the first section of the buried layer is formed with a larger thickness than the second section of the buried layer, the first section of the buried layer is formed to be concentric with and laterally surrounded by the second section of the buried layer, wherein the first section of the buried layer is formed to be aligned vertically below and in direct contact with the first well, and wherein the first section of the buried layer has a side boundary, and the side boundary of the first section of the buried layer is coplanar with the side boundary of the first well.