The annealing characteristics of 50‐keV (2–3) × 1011/cm211B+‐implantedp‐channel MOS transistors were investigated from 300 to 900°C. Below 500°C, the number of activated atomsNIIdecreased rapidly with decreasing anneal temperature and theC‐Vcharacteristics showed gradual distortions. This was presumably due to surface states induced by the ion implantation. Above 500°C,NIIincreased only slightly with increasing anneal temperature and the slope of theC‐Vcharacteristics in the transition region was larger than that of the unimplanted sample. Corresponding to the above features, the gain term increased near 500°C to a value about 30% larger than that of the unimplanted sample, while the breakdown voltage decreased below 500°C. Equivalent noise voltage decreased abruptly from 500 to 600°C. However, at lower drain current levels, the generation‐recombination noise spectrum did not disappear, even after a 900°C anneal. In addition, reverse‐annealing‐like phenomena were observed in the equivalent noise voltage between 350 and 450°C. The results of surface recombination velocity measurements were consistent qualitatively with the results of equivalent noise‐voltage measurements. Furthermore, device stability was confirmed by positive and negative bias‐temperature treatments (250°C, 1 h,Eox= ± 6.7 × 105V/cm) for devices annealed above 450°C.