A CMOS image sensor with an effectively increased aperture ratio and moreover with improved optical sensitivity, and a method of manufacture of such a CMOS image sensor is provided a first aspect of the invention is an image sensor, has a pixel region 10 in which are formed a plurality of pixels each having at least a photodiode, a reset transistor, and a source-follower transistor; and a peripheral circuit region 12 in which are formed peripheral circuits which process read-out signals read out from the pixel region, a well region PW2 in the pixel region PW1 is formed to be more shallow than a well region in the peripheral circuit region. Also, reset transistors or source-follower transistors are formed in the shallow well region PW2 of the pixel region 10, and a photodiode region PHD2 is embedded below the transistor well region PW2.