A chip includes a semiconductor substrate, a well region in the semiconductor substrate, and a transistor formed at a front side of the semiconductor substrate. A source/drain region of the transistor is disposed in the well region. A well pickup region is disposed in the well region, wherein the well pickup region is at a back side of the semiconductor substrate. A through-via penetrates through the semiconductor substrate, wherein the through-via electrically inter-couples the well pickup region and the source/drain region.