A semiconductor structure. The semiconductor structure includes a semiconductor substrate, a first transistor on the semiconductor substrate, and a guard ring on the semiconductor substrate. The semiconductor substrate includes a top substrate surface which defines a reference direction perpendicular to the top substrate surface. The guard ring includes a semiconductor material doped with a doping polarity. A first doping profile of a first doped transistor region of the first transistor in the reference direction and a second doping profile of a first doped guard-ring region of the guard ring in the reference direction are essentially a same doping profile. The guard ring forms a closed loop around the first transistor.