High volume productions of analog devices require usually more than one production facility. These facilities could be part of the company or in a foundry organization. A smart technology transfer is a key requirement to success. Nevertheless, small deviations of parametric key indices can lead to substantial differences in analog device performance. This paper describes an instructive case study to isolate the root cause of a parametric shift of a low drop output (LDO) voltage regulator. This shift caused a significant yield loss in one of the production facilities. The LDO shift was traced back to a current mirror mismatch. Physical failure analysis shows small differences in the gate oxide thickness which consequently vise versa led to threshold voltage mismatch. Further process analysis identified an unwanted topography in the silicon surface as the root cause of the non-uniform gate oxide growth.