Semiconductor image sensor device and fabrication method thereof

A semiconductor image sensor device, comprising:

• a semiconductor substrate comprising an image-sensing pixel region;
• a MOS transistor disposed on said semiconductor substrate within said image-sensing pixel region, wherein said MOS transistor comprises a source region, a drain region spaced apart from said source region, a channel region between said source region and said drain region, and a gate over said channel region;
• a salicide block (SAB) layer covering said MOS transistor and said image-sensing pixel region;
• a first interlayer dielectric (ILD) layer covering said SAB layer;
• a second ILD layer directly on said first ILD layer;
• a source contact on said source region, said source contact extending through said second ILD layer, said first ILD layer, and said SAB layer, and said source contact comprising a first doped polysilicon plug in said first ILD layer, a first salicide layer disposed on said first doped polysilicon plug, and a first conductive metal layer in said second ILD layer and on said first salicide layer;
• and
• a drain contact on said drain region, said drain contact extending through said second ILD layer, said first ILD layer, and said SAB layer, and said drain contact comprising a second doped polysilicon plug in said first ILD layer, a second salicide layer disposed on said second doped polysilicon plug, and a second conductive metal layer in said second ILD layer and on said second salicide layer.