Photoelectric conversion device and imaging system

A photoelectric conversion device comprising:

• a photoelectric conversion portion in a silicon layer having a light-receiving surface, the photoelectric conversion portion capable of producing electrons as signal charge carriers from light that has entered through the light-receiving surface,
• wherein the silicon layer includes an N-type first impurity region, a P-type second impurity region disposed opposite the light-receiving surface in a direction perpendicular to the light-receiving surface with respect to the first impurity region and containing boron and oxygen, and an N-type impurity region opposite the first impurity region in the direction perpendicular to the light-receiving surface with respect to the second impurity region, and the photoelectric conversion portion includes at least a part of the first impurity region and at least part of the second impurity region, and
• wherein the second impurity region includes a first portion having an atomic boron concentration that is the highest of the portions opposite the light-receiving surface with respect to the first impurity region, a second portion opposite the first impurity region in the direction perpendicular to the light-receiving surface with respect to the first portion, and a third portion located on the same side as the first impurity region in the direction perpendicular to the light-receiving surface with respect to the first portion and having an atomic boron concentration Bc and an atomic oxygen concentration Oc, the third portion satisfying the relationship 1×1046≤Bc×Oc2≤1×1050.