A new method for the DRAM soft-error evaluation was developed. By using a focused proton microprobe as a radiation source, and scanning it on a memory cell plane, local sensitive structure of memory cells against soft-errors could be investigated with a form of the susceptibility mapping. Cell mode and bit-line mode soft-errors could be clearly distinguished by controlling the incident location and the proton dose, and it was also found that the incident beam within 4 µm around the monitored memory cell caused the soft-error. The retrograde well formed by the MeV ion implantation technology was examined by this method. It was confirmed that the B+ layers in the retrograde well were a sufficient barrier against the charge collection. The generation rate of the electron-hole pairs and the charge collection into n+ layers with a retrograde well and a conventional well were estimated by the device simulator, and were explained the experimental results.