| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor device which can shorten a turn around time of a mask ROM. SOLUTION: An inter-layer insulating film 39 is formed on an MOS transistor forming a memory cell transistor. Thereafter concurrent to formation of a contact hole 41A above a P+ source layer 36, and an ion-plantation hole 41B for ROM writing is formed on a gate electrode 34 of the MOS transistor. And boron (11B+) ions are implanted into a channel region 38 through the contact hole 41A and ion-implantation hole 41B to perform the ROM data writing and to form a P++ type plug implantation layer 42 on the source layer 36 at the bottom of the contact hole 41A, thus increasing a P-type impurity concentration. |
