The n+-type semiconductor regions 9 b, 9 c and the n???-type semiconductor regions 9 d, 9 d are all formed by introducing, for example, phosphorus or arsenic into the p-well 1PW. The n???-type semiconductor regions 9 d, 9 d is a region mainly serving as a semiconductor region for DD. In the n???-type semiconductor regions 9 d, 9 d, the ends at the channel sides of the MIS's Qt1, Qt2 for selection