| 摘要 |
PURPOSE:To realize a highly integrated memory by using three or more masks having different mask patterns from one another for providing a plurality of gate electrodes. CONSTITUTION:By means of an ion implantation technique or the like, a plural ity of doped layers 6, 7 are formed by diffusion for controlling two different threshold values of gate electrodes. First gate electrodes 9 are formed through a first gate insulating film 8 by using a mask pattern adapted such that the first gate electrodes are formed on every other doped layers 6 and 7. Then, by using a second mask pattern, second gate electrodes 11 are formed on every other layers on which the first gate electrodes have not been formed, through a gate insulating film 10. Finally, by using a third mask pattern, third gate electrodes 14 are formed on the rest of the doped layers through a third gate insulating film 13. In this manner, memories can be integrated at a high density at good yield. |
