| 摘要 |
PURPOSE:To control a threshold voltage value accurately, by constituting a plurality of MISFETs having double gates of polySi and metal or silicide with the polarity of the polySi gates as of a p<+>-type or an n<+>-type. CONSTITUTION:A plurality of bit transistors B-Tr1-B-Tr4 and the like, are connected in series in the direction perpendicular to word lines on a p<->-type Si substrate 1. All the said transistors are formed as n-MOSFETs having double- gate electrodes (word lines WL1-WL4) comprising p<+>-type polySi gates 10A-10D and the like, which include high concentration boron in a saturated state beforehand, and metal titanium layers 11. When fixed information is written, a mask film 7 having holes is formed on the desired bit transistors B-Tr1 and B-Tr3. phosphorus ions are implanted through the holes in the film 7, and n<+>-type polySi gates 12A and 12C are formed. |
