Abstract: A method for manufacturing mask ROMs is disclosed, wherein a semiconductor substrate of a first conductive type, on which a gate insulating layer, a poly-silicon layer, source and drain regions and a spacer are formed is stored after depositing the entire surface of the structure with a protection layer until the next steps such as programming, so that the poly-silicon gate and the source and drain regions of the structure can be prevented from being polluted with organisms or matriums, etc. by forming a protection layer before the storage, thereby improving the efficiency and reliability of mask ROMs, and the ROM data region can be checked during the etching of the protecting layer for distinguishing the defective chips simply and efficiently in a short manufacturing time.