| 摘要 |
PURPOSE:To shorten the turn-around time by changing a depletion type MISFET into an enhancement type or a weak depletion type by the channel doping of an impurity having small mass and writing information to a memory cell. CONSTITUTION:MISFETs constituting a memory cell array M-ARY are all organized to a depletion type (corresponding to information such as one 1) through channel doping by the ion implantation of a substance such as phosphorus previously. Channel doping by the ion implantation of a substance such as boron is conducted to a channel section in the depletion type MISFET corresponding to a memory cell to which information such as one 0 must be written, thus turning the depletion type MISFET into an enhancement type or a weak depletion type (the small absolute value of threshold voltage), then writing desired information. Accordingly, the turn-around time of a vertical ROM to which desired information is written can be shortened. |
