Patent ID: 8053342

Claim:
A method of fabricating a mask ROM device, the method comprising: forming an on-cell gate insulating film and an off-cell gate insulating film on a substrate; forming an on-cell gate electrode on the on-cell gate insulating film; forming an off-cell gate electrode on the off-cell gate insulating film; performing a first ion implantation process and a second ion implantation process using ions of a first polarity to form a first on-cell ion implantation region, a first off-cell ion implantation region, a second on-cell ion implantation region and a second off-cell ion implantation region, wherein the first and second on-cell ion implantation regions are aligned with a side surface of the on-cell gate electrode and wherein the first and second off-cell ion implantation regions are aligned with a side surface of the off-cell gate electrode; performing a third ion implantation process using ions of a second polarity to form a third on-cell ion implantation region that is aligned with the side surfaces of the on-cell gate electrode and the off-cell gate electrode; forming gate spacers on the side surfaces of the on-cell gate electrode and the off-cell gate electrode; and performing a fourth ion implantation process to form a fourth on-cell ion implantation region and a third off-cell ion implantation region that are aligned with the gate spacers.