PURPOSE: To obtain a data injection means of MASK-ROM suitable also for shortening of TAT(Turn Around Time) and reliable by applying an electron beam to a channel part of a memory cell.

CONSTITUTION: Since an electron has a small diameter and passes easily through an oxide film or the like, electrons 10 in a necessary amount can be made to reach a channel part 9 by a relatively small injection energy and in a relatively short time even when they are injected at a position being far from the channel part 9. The electrons reaching the channel part 9 destruct a channel interface and cause a state of leak between a source and a drain. Accordingly, a depletion-type transistor can be made. According to this method, a data injection means of MASK-ROM suitable also for shortening of TAT and more reliable can be attained.