The current work is devoted to studying the evolution of deep level defects in the lower half of the 4H-SiC bandgap after high temperature processing and ion implantation. Two as-grown and pre-oxidized 4H-SiC sets of samples have been thermally treated at temperatures up to 1950 C for 10 min duration using RF inductive heating. Another set of as grown samples was implanted by 4.2 MeV Si ions at room temperature (RT) with different doses (1-4× 10 8 cm-2). The so-called “D-center” at E V+ 0.6 eV dominates and forms after the elevated heat treatments, while it shows no change after the ion implantations (E V denotes the valence band edge). In contrast, the concentration of the so-called HK4 level at E V+ 1.44 eV increases with the implantation dose, whereas it anneals out after heat treatment at≥ 1700 C.