The analysis of shallow p-n junctions by standard secondary ion mass spectrometry with oxygen primary ion bombardment can be significantly enhanced in two ways. The sensitivity can be increased about 100-fold by using both instrumental means and chemical modification (in situ oxidation). The depth resolution can be improved about twofold in many cases (e.g., for B), by phenomena accompanying oxidation. It is known that chemical segregation of As may adversely affect depth resolution, so analyses for different elements must be treated on a case-by-case basis.