An image sensor includes a substrate having a photoelectric conversion element therein, a first via extending into a first surface of the substrate such that a first upper surface of the first via is exposed adjacent the first surface of the substrate, a second upper surface of the first via extending away from the first surface of the substrate, first to third insulating films sequentially stacked on the first surface of the substrate, and a contact extending through the first to third insulating films and into the second upper surface of the first via. The contact includes a first portion within the first via, a second portion in the first insulating film, a third portion in the second insulating film, and a fourth portion in the third insulating film.