| 摘要 |
PURPOSE:To shorten a period to be consumed from a coding step to a final step by removing an interlayer insulating film formed on a ROM region, selec tively ion implanting lower part of a gate electrode of a previously selected MOS type transistor of a MOS type transistor formed on the removed region, and forming a coding layer. CONSTITUTION:A gate insulating layer 13, a gate electrode 14 and a diffused layer 12 are sequentially formed on a silicon substrate 11 to form a MOS type transistor. Then, silicon nitride is deposited to form a protective insulating layer 15. Silicon oxide is deposited on the layer 15 to form an interlayer insult ing layer 16. Thereafter, a wiring layer 17 is formed. Subsequently, part except a ROM region is masked with photoresist 18, and the layer 16 of the ROM region is removed by using fluoric acid etchant. In this case, the layer 15 is not almost etched. After the etching is finished, the photoresist 18 is peeled. Then, photoresist 19 is pattern-formed in alignment with a coding pattern, with it as a mask impurity ions are implanted to form a coding layer 20 at the lower part of the gate electrode. |
