A brief introduction reviews the changes that have occurred in semiconductor wafer processing, which, coupled with developments in X ray Photoelectron Spectroscopy, XPS, instrumentation, have led to XPS becoming a primary materials analysis tool in this industry. Three specific examples illustrating the use of XPS and Angle resolved XPS, ARXPS, are then presented. These are nitridation processing of high k gate material (HfO2 based); the monitoring of Al content and chemistry in a 10A TiAlN film (a metal gate add on process to high k); and deposition of diamond-like amorphous C films (a candidate for hard mask applications in DRAM, NAND flash, and NOR flash memories).