Image sensor and method of manufacturing the same

An apparatus comprising:

• a first epitaxial layer formed over a semiconductor substrate.
• a first photodiode formed in the first epitaxial layer;
• a second epitaxial layer formed over the first epitaxial layer;
• a second photodiode formed in the second epitaxial layer;
• a first plug formed in the second epitaxial layer;
• a third epitaxial layer formed over the second epitaxial layer;
• a plurality of isolation layers formed over the third epitaxial layer for separating an isolation region and an active region;
• a plurality of second plugs formed in the third epitaxial layer adjacent to and in direct contact with a respective one of the plurality of isolation layers;
• a third photodiode formed in the third epitaxial layer;
• and
• a gate structure formed over the third epitaxial layer,
• wherein the uppermost surface of the third photodiode is exposed.

A method for forming an image sensor, the method comprising the steps of:

• forming a first epitaxial layer over a semiconductor substrate;
• forming a first photodiode in the first epitaxial layer;
• forming a second epitaxial layer over the first epitaxial layer and the first photodiode;
• forming a second photodiode in the second epitaxial layer;
• forming a third epitaxial layer over the second epitaxial layer and the second photodiode;
• and
• burying a third photodiode in the third epitaxial layer.