| 摘要 |
<p>PURPOSE:To realize high-speed operation, to miniaturize a memory and to shorten a manufacture period by storing data by lowering the threshold level of a cell by ion-implantation. CONSTITUTION:Ion-implantation is carried out only as to a cell expected to be stored with, for example, ''0''. A cell expected to be stored with ''1'' is not ion- implanted, but left in the same state as transistors Q12 and Q22 of a memory peripheral circuit. Then, n-type impurities such as phosphorus are implanted in n- channel FET whose silicon semiconductor substrate SUB is of type (p). Consequently, p-type impurity density of the channel lowers and the threshold level also decreases, realizing the depletion type. For example, the threshold level of the cell without ion-implantation is set to +1V, and that of cell Cej ion-implanted to -4V, thereby storing data in Cej.</p> |
