The invention discloses a chip package and a method for forming the same. The chip package includes a first substrate having an upper surface, a lower surface and a sidewall. A sensing region or device region and a conducting pad are adjacent to the upper surface. A through-hole penetrates the first substrate. A redistribution layer extends from the lower surface into the through-hole and is electrically connected to the conducting pad. The redistribution layer further laterally extends from the lower surface to protrude from the sidewall. The method not only may increase the sensing sensitivity of the chip package, but also may reduce the size of the chip package.