An image sensor formed in a semiconductor stack of a lower region of a first conductivity type and of an upper region of a second conductivity type, including: a photodiode formed of a first portion of the stack; a read area formed of a second portion of the stack; a trench with insulated walls filled with a conductive material, the trench surrounding the photodiode and the read area and being interrupted, all along its height, on a portion facing the photodiode and the read area; and first connection mechanism associated with the conductive material of the trench and capable of being connected to a reference bias voltage.