In this paper, the total ionizing dose (TID) response of a commercial 28-nm high-k CMOS technology at ultrahigh doses is measured and discussed. The degradation of pMOSFETs depends not only on the channel width but also on the channel length. Short-channel pMOSFETs exhibit a higher TID tolerance compared to long ones. We attributed this effect to the presence of the halo implantations. For short-channel lengths, the drain halo can overlap the source one, increasing the average bulk doping along the channel. The higher bulk doping attenuates the radiation-induced degradation, improving the TID tolerance of short-channel transistors. The results are finally compared and discussed through technology computer-aided design simulations.