Image sensing device and manufacturing method thereof

A back side illuminated (BSI) image sensor, comprising:

• a semiconductive substrate;
• a pixel region and a logic region in the semiconductive substrate;
• a transistor disposed at a front side of the semiconductive substrate in the pixel region, wherein
• the transistor comprises a gate structure and at least a source region or a drain region;
• a nitride layer and an oxide layer overlying the gate structure and at least the source region or the drain region;
• a logic transistor dispose in the logic region, wherein
• the logic transistor comprises a logic gate structure and at least a logic source region or a logic drain region;
• a dielectric layer above the front side of the semiconductive substrate;
• and
• a color filter disposed at a back side of the semiconductive substrate.

A back side illuminated (BSI) image sensor, comprising:

• a semiconductive substrate having a front side;
• a first transistor comprising:
• a first gate structure over the front side;
• a first gate spacer over a first side wall of the first gate structure;
• a first source or drain region under the front side and adjacent to the first side wall, and the first source or drain region comprising a photo-sensitive element;
• and
• a first gate spacer extension extended from the first gate spacer and covering the first source or drain region, wherein
• each of the first gate spacer and the first gate spacer extension comprises:
• a first portion of a first oxide layer and a second portion of the first oxide layer, respectively;
• and
• a first portion of a nitride layer and a second portion of the nitride layer, respectively;
• the nitride layer covers the first oxide layer.