PURPOSE: To obtain a ROM having consistent characteristics by making the reference cell of the current mirror type sense amplifier out of the reference cell combination which makes the gates out of the selection line of a memory cell combination to read, the same selection line as a word line, and the word line.

CONSTITUTION: The reference cells consist of NMOS memory cell depression type 2-4, etc., and NMOS 1, etc., for selection. They make as gate input the selection lines such as memory cell combination 5-8, the same selection line 17 as the word line, and the word lines 18-20. Therefore, the gate potential is made equal between the memory cell combination 5-8, etc., to read out and the memory cell combination 1-4, etc., for reference. Also, the memory cell combination 1-4, etc., for reference may be placed in the matrix of the memory cells, and the dispersion at the time of manufacturing is minimized. Thus, the ROMs having consistent characteristics are obtained.