Alignment mark structure and method of fabricating the same

A fabricating method of an alignment mark structure, comprising:

• providing a dielectric layer;
• forming a trench embedded in the dielectric layer;
• forming an alignment mark filling up the trench, wherein the alignment mark comprises:
• a metal layer covering the trench;
• a first material layer covering and contacting the metal layer;
• a second material layer covering and contacting the first material layer;
• and
• a third material layer covering and contacting the second material layer;
• wherein the first material layer, the second material layer, and the third material layer independently comprises silicon nitride, silicon oxide, tantalum-containing material, aluminum-containing material, titanium-containing material, or a low-k dielectric having a dielectric constant smaller than 2.7, and a reflectance of the first material layer is larger than a reflectance of the second material layer, the reflectance of the second material layer is larger than a reflectance of the third material layer.