Control of charge carrier collection by high-energy boron-implanted layers has been investigated to clarify the validity of buried well structures against soft errors in dynamic random-access memories (DRAMs) by ion-induced-current measurements using high-energy proton microprobes. A finely focused 1.3 MeV proton beam has been used to irradiate normal to n+p diodes with buried layers fabricated by B+ implantation at 160 — 1000 keV and to doses of 1 × 1012 — 1 × 101 ions/cm2, and reverse-biased at 1 to 5 V. The measured current was induced by carriers generated by ion microprobes. The collection of charge carriers induced by microprobe irradiation could be reduced by a buried layer formed by boron implantation. It was found that the rate of charge collection depended not on the depth but on the implantation dose of the buried layer. The carrier collection efficiency of the n+p diode with twin wells (i.e., a retrograde well) was two thirds of that with a conventional well.