An imaging device includes a first semiconductor element including at least one bump pad that has a concave shape. The at least one bump pad includes a first metal layer and a second metal layer on the first metal layer. The imaging device includes a second semiconductor element including at least one electrode. The imaging device includes a microbump electrically connecting the at least one bump pad to the at least one electrode. The microbump includes a diffused portion of the second metal layer, and first semiconductor element or the second semiconductor element includes a pixel unit.