Patent ID: 7344964

Claim:
A method for fabricating an image sensor, comprising: forming a gate structure on a semiconductor layer of a first conductive type; performing a first ion implantation process to form a first impurity region of the first conductive type aligned with one side of the gate structure and extending to a first depth from a surface of the semiconductor layer; forming a first spacer on each sidewall of the gate structure; performing a second ion implantation process to form a second impurity region of the first conductive type aligned with the first spacer and extending to a second depth that is larger than the first depth from the surface of the semiconductor layer; forming a second spacer on each sidewall of the first spacer; performing a third ion implantation process to form a third impurity region aligned with the second spacer and extending to a third depth that is larger than the second depth from the surface portion of the semiconductor layer; and performing a fourth ion implantation process to form a fourth impurity region of a second conductive type beneath the third impurity region.