Future Si microelectronic devices will require increasingly stringent limits on transition-metal impurities. There is thus a need to develop new methods for impurity gettering that rely on gettering sites that are active for arbitrarily small impurity concentrations, below the characteristic solid solubility at which metal suicides precipitate. These sites must also be highly preferred relative to solution sites in the Si matrix even at elevated temperatures. One such method has been developed that is also expected to be compatible with front (device) side gettering enabling smaller diffusion lengths for lower processing temperatures. This method involves boron implantion in the front side to levels above the boron-saturation limit and annealing to generate the gettering sites. The gettering layer is introduced at a depth beneath the device zone through appropriate choice of implantation energy. SIMS compositional profiling shows transition metals are strongly gettered within the boron-supersaturated layer. The purpose of this study was to identify the structure and composition of the gettering sites within the boron-supersaturated layer.