MANUFACTURE OF MASK READ ONLY MEMORY

PURPOSE:To shorten the term of the works and to reduce the cost by forming contact holes and implanting holes for writing ions in an interlayer insulating film, and then by implanting writing ions using the interlayer insulating film as a mask. CONSTITUTION:Not only contact holes 20-33 but also a hole 24 for implanting writing ions B are formed in a PSG film 13 using a photoresist layer 14, and writing ions are implanted using the said photoresist layer 14 and the PSG film 13 as masks. Accordingly, a photoresist process using photomasks solely for the purpose has become unnecessary, and shortening the term of the works and reducing the cost can be realized. Besides, writing ions, B, can be implanted by masking only the PSG film 13, after removing the photoresist layer 14.