A method of fabrication of a photosensitive device is disclosed. A substrate with at least an insulator layer formed thereon is provided. The insulator layer comprises a plurality of photoreceiving regions, and a plurality of conductive patterns are formed thereon without covering the photoreceiving regions. A dielectric layer is formed on the insulator and the conductive patterns, and polished by CMP thereof. The dielectric layer comprises a first dielectric layer formed by PECVD and a second dielectric layer formed by HDPCVD.