The spectral responsivity of 4H-SiC photodiodes was studied and optimized in this paper with the aim to realize UV photo-sensors, selectively sensitive either to harder or to softer UV radiation. The spectral selectivity of the SiC-photodiodes was achieved by optimizing doping profiles in the active regions of the photodiodes and of the anti-reflective coating. A shallow doping profile of the p+-emitter allowed an enhancement of sensitivity for hard UV radiation. Deeper doping profiles were chosen for detection of softer UV radiation. The impact of the variations of the thickness of protective and anti-reflective layers was studied as well.