| 摘要 |
PURPOSE:To improve the protective capability of overvoltage by making the threshold voltage of a parasitic MOS-FET for protection lower than that of other parasitic MOS-FETs and higher than that of an input MOS-FET. CONSTITUTION:The thickness d2 of a field oxide film 7 in a region constituting a parasitic MOS-FET Q2 for protection is made thinner than that of field oxide films in other sections. Consequently, the threshold voltage of Q2 is lower than that of other parasitic MOS-FETs. However, the threshold voltage Q2 is higher than that of Q1 because the field oxide film in Q2 is far thicker than a gate oxide film. Accordingly, an MOS-FET integrated circuit device having high overvoltage protective capability is obtained by using the MOS-FET Q2 having low threshold voltage as a protective element. |
