Imaging element with bonded chips or substrates and method for manufacturing imaging element

An imaging element, comprising:

• a plurality of semiconductor chips each having a semiconductor substrate and a wiring region and bonded to each other,
• wherein one of the plurality of semiconductor chips is provided with a photoelectric conversion unit for performing photoelectric conversion of incident light,
• wherein two of the plurality of semiconductor chips are provided with first pads,
• wherein first surfaces of wiring regions of the two semiconductor chips are bonded to each other,
• wherein the first pads are arranged on the first surfaces of the wiring regions and are bonded to each other,
• wherein at least a first one of the two semiconductor chips is provided with a second pad on a second surface of the wiring region of the first one of the two semiconductor chips,
• wherein the second pad has a protrusion formed thereon so as to face toward the bonded surface,
• wherein the second surface of the wiring region of the first one the two semiconductor chips is opposite the first surface of the wiring region of the first one of the two semiconductor chips,
• wherein the protrusion of the second pad of the first one of the two semiconductor chips extends to a point between the first and second surfaces of the wiring region of the first one of the two semiconductor chips and is spaced apart from the first surface of the wiring region of the first one of the two semiconductor chips,
• wherein a side surface of the first pad of the first one of the two semiconductor chips, a side surface of the second pad of the first one of the two semiconductor chips, and the protrusion of the second pad of the first one of the two semiconductor chips are formed in a same insulating film layer, and
• wherein the second pad is configured to have a size different from a size of the first pad.