Active photosensitive structure with buried depletion layer

A method of operating a pixel sensor cell, comprising:

• generating charges in response to applied light reaching a photosensitive element formed in a substrate;
• accumulating the generated charges in a charge accumulation region buried beneath a top surface of the substrate;
• and
• determining a resistance of a JFET channel region located beneath said top surface of the substrate but above said charge accumulation region, said JFET channel region having a changeable resistance dependent upon the charges in the accumulation region;
• and
• producing a signal based on the resistance of said JFET channel region.

A method of operating a pixel sensor cell, comprising:

• generating charges in response to applied light reaching a photosensitive element formed at least partially in a substrate;
• accumulating the generated charges in a charge accumulation region comprising a JFET gate region buried beneath a top surface of the substrate;
• and
• determining a resistance of a JFET channel region located beneath the top surface of the substrate but over said JFET gate region, said JFET channel region having a resistance characteristic that changes in response to the amount of charge accumulated in said JFET gate region;
• reading out a signal from a first contact electrically connected to said JFET channel region, the signal representing a current flowing through the JFET channel region;
• and
• draining the accumulated charges from said charge accumulation region to a drain region.