Solid-state image sensor and method of manufacturing the same

A solid-state image sensor which includes a semiconductor layer having a first surface and a second surface, comprising:

• charge accumulation region pairs arranged between the first surface and the second surface, each of the charge accumulation region pairs including charge accumulation regions each configured to accumulate charges;
• microlenses arranged on a side of the second surface so that one of the microlenses is assigned to one of the charge accumulation region pairs;
• a first isolation portion arranged between the charge accumulation regions of one of the charge accumulation region pairs, the first isolation portion including a first isolation region extending along a direction connecting the first surface and the second surface, the first isolation region including a first part and a second part, the first part being nearer the first surface than the second part;
• and
• a second isolation portion arranged between the charge accumulation region pairs, the second isolation portion including a second isolation region extending along the direction, the second isolation region including a third part and a fourth part, the third part being nearer the first surface than the fourth part,
• wherein a width of the first part is smaller than a width of the second part, and a width of the third part is smaller than a width of the fourth part.