System and method for determining a respective effective oxide thickness for each of first and second dielectric structures that form a MOS (metal oxide semiconductor) stack. A first plurality of test MOS (metal oxide semiconductor) stacks are formed, and each test MOS stack includes a respective first dielectric structure comprised of a first dielectric material and a respective second dielectric structure comprised of a second dielectric material. A respective deposition time for forming the respective first dielectric structure corresponding to each of the first plurality of test MOS stacks is varied such that a respective first effective oxide thickness of the respective first dielectric structure varies for the first plurality of test MOS stacks. A respective second effective oxide thickness of the respective second dielectric structure is maintained to be substantially same for each of the first plurality of test MOS stacks. A respective total effective oxide thickness, EOTMOS, is measured for each of the first plurality of test MOS stacks. A first graph having total effective oxide thickness as a first axis and having deposition time for forming the first dielectric structure as a second axis is generated by plotting the respective total effective oxide thickness, EOTMOS, versus the respective deposition time for forming the respective first dielectric structure for each of the first plurality of test MOS stacks. The respective second effective oxide thickness of the respective second dielectric structure that is substantially same for each of the first plurality of test MOS stacks is determined from an intercept of the first axis of total effective oxide thickness when deposition time for forming the first dielectric structure of the second axis is substantially zero in the first graph.