Mechanisms for forming image-sensor device with deep-trench isolation structure

A method of fabricating an image-sensor device, comprising:

• forming a radiation-sensing region and a doped isolation region in a semiconductor substrate, wherein the doped isolation region is adjacent to the radiation-sensing region;
• forming a recess in the doped isolation region;
• and
• forming a negatively charged film over an interior surface of the recess.

A method of fabricating an image-sensor device, comprising:

• forming a radiation-sensing region and a doped isolation region in a semiconductor substrate, wherein the doped isolation region is adjacent to the radiation-sensing region;
• thinning the semiconductor substrate such that the radiation-sensing region and the doped isolation region are exposed;
• partially removing the doped isolation region to form a recess;
• and
• forming a negatively charged film over an interior surface of the recess and a surface of the radiation-sensing exposed after the thinning of the semiconductor substrate.