A stacked structure includes a first die bonded over a second die. The first die has a first die area defined over a first surface. At least one first protective structure is formed over the first surface, around the first die area. At least one side of the first protective structure has at least one first extrusion part extending across a first scribe line around the protective structure. The second die has a second die area defined over a second surface. At least one second protective structure is formed over the second surface, around the second die area. At least one side of the second protective structure has at least one second extrusion part extending across a second scribe line around the protective structure, wherein the first extrusion part is connected with the second extrusion part.