Pixel with anti-blooming circuitry formed in shallow trench isolation

Abstract

A pixel of an image sensor may include an anti-blooming (AB) transistor with a gate formed in a shallow trench isolation (STI) of the pixel. The STI is positioned within the horizontal boundaries of the pixel structure. In certain instances, the STI isolates the drain region for a reset transistor of the pixel from a photodiode of the pixel and the AB transistor shares the drain region with the reset transistor. In such instances, the AB transistor may be turned on and provided a higher potential than the photodiode through its gate voltage to drain excess photoelectrons from the photodiode and prevent blooming due to oversaturation of the photodiode. In some instances, the gate of the AB transistor is formed in a separate STI and has its own drain formed next to the gate in the STI with the higher potential being provided through the gate or drain voltage.