| 摘要 |
A method for fabricating a semiconductor memory device which includes a single substrate, at least one memory cell including at least one MOS transistor formed on the single substrate, and a peripheral circuit having at least one MOS transistor formed on the single substrate, comprises the steps of forming on the single substrate a gate electrode for each of the MOS transistors of the memory cell and the peripheral circuit, iono-implanting impurities at a low dosage by using the gate electrodes as a mask so as to forming a low impurity concentration of source/drain regions of the MOS transistors of the memory cell and the peripheral circuit, depositing a mask layer to cover an area of the memory cell, and ion-implanting impurities at a high dosage by using the mask layer as a mask, so as to dope impurities to only the source/drain regions of the MOS transistor of the peripheral circuit, so that the MOS transistor of the memory cell has the source/drain regions of a low impurity concentration, and the MOS transistor of the peripheral circuit has the source/drain regions including a high impurity concentration portion.
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