| 摘要 |
PURPOSE:To make one memory memorize two values and more of data by a method wherein an MNOS element and a floating gate type element are combined with each other providing two kinds of charge depositing regions such as a trap around the interface between an SiO2 film and an Si3N4 film and a floating gate. CONSTITUTION:The N layers 2, 3 are provided on a P type Si substrate 1 and an Si3N4 film 6 and successively a floating gate 9, a control gate 8 are laminated as specified respectively through the intermediary of an SiO2 film 7 and another SiO2 film 10. In case of writing, the layers 2, 3 and the substrate 1 are grounded to capture electrons around the films 6, 7 supplying the control electrode 8 with positive high voltage. In case of erasing, if the electrode 8, the layer 3 and the substrate 1 are grounded supplying a drain 2 with positive high voltage, only the charge in the gate 9 is erased while if the electrode 8 is grounded supplying the substrate 1 with positive high voltage, the captured electrons on the interface between the films 6, 7 are erased. In such a constitution, a memory device may be provided with a threshold value voltage with 3 values making one memory memorize 2 values and more of data by means of combining the charge plus (21) and minus (22) of the floating gate 9 with the captured charge plus (23) and minus (22) around the interface between the films 7, 6. |
