| 摘要 |
PURPOSE:To obtain the fixed memory storage, the area of a fixed memory cell thereof is small, in a short time by previously implanting ions in a channel through a gate electrode and writing information in a desired IGFET among IGFETs for the cell. CONSTITUTION:The IGFETs Tr1-Tr3 are formed onto a P type Si substrate 11 through isolation by field oxide films 12, the surface is coated with an insulating film 31, and an intermediate product is manufactured. The insulating film 31 on a Tr2 poly Si gate 30 is opened by a resist mask 32 in response to a writing information after the reception of an order, ions are implanted in the channel between a source and a drain through a poly Si gate and a gate oxide film, threshold voltage is changed, a desired information is written and the ROM is completed. An insulating film is reformed onto the gate of the Tr2. In the ROM such as an NAND type ROM, P ions are implanted in the channel of the Tr2 writing[O]and the Tr2 is brought to an ON state, and the Tr3 writing[1]is protected from ions by the resist 32 and the insulating film 31 and brought to an OFF state. According to this constitution, the ROM having the high degree of integration is obtained in a short time. |
