Semiconductor device and manufacturing method thereof

A semiconductor device, comprising:

• a supporting substrate;
• a semiconductor layer disposed over the support substrate and including a first main surface and a second main surface opposing the first main surface;
• a plurality of light receiving elements which are formed in the semiconductor layer and in each of which photoelectric conversion is performed;
• a light receiving lens disposed over the second main surface of the semiconductor layer to supply light to each of the light receiving elements;
• and
• a mark for alignment formed inside the semiconductor layer,
• wherein the mark for alignment extends from the first main surface toward the second main surface,
• wherein the mark for alignment includes a protruding portion formed so as to protrude from the second main surface in a direction toward where the light receiving lens is disposed,
• wherein a bottom surface of the mark is coplanar with the first main surface of the semiconductor layer, and
• wherein the mark is made of a same material as the semiconductor layer and is in direct contact with the semiconductor layer.