During high temperature device processing of 4H-SiC wafers heavily doped with nitrogen, visible signs of severe deformation were observed in certain regions of the wafers. The deformation was not uniform throughout but was localized in certain regions; most of the wafer did not show any visible change after processing. In addition, secondary ion mass spectrometry (SIMS) measurements showed a non-uniform nitrogen doping gradient across the wafer with the affected regions of the wafer having a higher nitrogen concentration than the non-faulted regions. In this paper, a conventional and high-resolution transmission electron microscopy (TEM) examination of the microstructures of the affected and non-affected regions of a wafer having undergone this particular processing route is reported. While no defects were observed by TEM from the thin foils prepared from the non-affected region, a high density of stacking faults was observed in specimens made from the affected region. An examination of a few of the defects by HRTEM showed them all to be double-layer stacking faults that may have formed by the glide of Shockley partial dislocations on neighboring basal planes. It appears that in the affected regions of the wafer, the n-doping had pushed the Fermi level to a value above the stacking fault energy level thus making a faulted crystal energetically favorable.