Advances in memory IC technology for dynamic random access memory (DRAM) devices have come about from a reduction in individual cell thickness with a corresponding increase in cell depth in order to maintain the same stored capacitance value. As the memory size on DRAM devices rises, memory cells must get deeper making the process of measuring depth more difficult. In this article we describe a novel, nondestructive, noncontact metrology technique which utilizes both two‐dimensional diffraction analysis and multivariate statistical methods to measure deep trench depth in the 6–9 μm range. We applied this technique to two DRAM product wafers and obtained a successful prediction of trench depth for both wafers with an accuracy of ±0.04 μm, or ±0.56% variation relative to scanning electron microscope measurements of the same samples.