Methods of selectively etching BPSG over TEOS are disclosed. In one embodiment, a TEOS layer may be used to prevent contamination of other components in a semiconductor device by the boron and phosphorous in a layer of BPSG deposited over the TEOS layer. An etchant of the present invention may be used to etch desired areas in the BPSG layer, wherein the high selectivity for BPSG to TEOS of etchant would result in the TEOS layer acting as an etch stop. A second etchant may be utilized to etch the TEOS layer. The second etchant may be less aggressive and, thus, not damage the components underlying the TEOS layer.