field isolation between arrayed picture cells of an image sensor is fabricated thinner than the insulation layer for the peripheral portion of ccd operatively connected to picture cells . the field isolation is fabricated by a selective thermal oxidization , by which the isolation film inflates not only vertically but also laterally , therefore the thinner isolation layer can be narrower . and , the lower applied voltage to the picture cell than applied voltage to the ccd portion allows the narrower isolation . the narrower field isolation between the picture cells allows greater density of integration of the picture cells . procedures to embody the invention are disclosed , one of which is to fabricate the thinner isolation first , and another one is the thicker insulation layer first .