Stacked cmos image sensor and method of manufacturing the same

An image sensor comprising:

• a first substrate;
• a photodiode and a first transistor adjoining on the first substrate;
• a second substrate underlying the first substrate;
• and
• a second transistor on the second substrate;
• wherein the photodiode and the first and second transistors form a pixel sensor, and wherein a body of the first transistor and an anode of the photodiode are electrically coupled together and are electrically isolated from a body of the second transistor.

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

• forming a first integrated circuit (IC) chip, comprising:
• forming a photodiode in a first semiconductor substrate;
• forming a first transistor on the first semiconductor substrate, adjacent to the photodiode, the photodiode and the first transistor forming a first pixel-sensor portion;
• forming a second IC chip, wherein the forming of the second IC chip comprises forming a plurality of second transistors on a second semiconductor substrate, and wherein the second transistors form a second pixel-sensor portion;
• and
• bonding the first and second IC chips together such that the first and second pixel-sensor portions are stacked and electrically coupled together to form a pixel sensor;
• wherein a bulk of the first semiconductor substrate and a bulk of the second semiconductor substrate are electrically isolated from each other at completion of the bonding.