In a MONOS memory of the split-gate type formed by a field effect transistor formed on a fin, it is prevented that the rewrite lifetime of the MONOS memory is reduced due to charges being locally transferred into and out of an ONO film in the vicinity of the top of the fin by repeating the write operation and the erase operation. By forming a source region at a position spaced downward from a first upper surface of the fin in a region directly below a memory gate electrode, the current is prevented from flowing concentratedly at the upper end of the fin.