Defects due to process-design interaction have a systematic nature. Therefore they can have a profound impact on yield. The capability to detect (and correct) them is a requirement to continue to follow Moore?s law. Most of the systematic defects are detected during the process development. These defects are detectable with test structures or visual inspection tools. However some process marginalities will only show-up in the topology of ?real? designs. Moreover, these defects are often not detectable with stuck-at testing. We show two examples of process related defects which could only be detected with more advanced test methods such as transition fault testing and low voltage testing. To correct systematic problems, however, one should not only have the capability to detect defects but also to identify them. Our examples show that other tests would have been far more sensitive in detecting systematic issues. Therefore the detection of systematic defects gives new requirements to test suites and can only be achieved with a shift in the position of manufacturing test.