| 摘要 |
PURPOSE:To select a connection or a disconnection between a built-in resistance and an input/output terminal by implanting an impurity by a method wherein the built-in resistance is installed between the input/output terminal to an external device and a power-supply terminal for the built-in resistance and the impurity is implanted. CONSTITUTION:A built-in resistance R is inserted between a P-MOS transistor(T) 1 and a power-supply terminal P1 for the built-in resistance. This built-in resistance R is formed by implanting a group III substance such as boron or the like. Since this process is executed prior to a gate process, no obstacle, exists and the built-in resistance R of an accurate resistance value can be formed. The channel width of the P-MOS T1 is set to be wide and an internal resistance value during the continuity becomes considerably smaller than the resistance value of the built-in resistance R. A connection or a disconnection between the built-in resistance R and an input/output terminal P2 is selected according to whether the group III substance is implanted in the channel region of the P-MOS T1 having an ordinary characteristic. Because the internal resistance value of the P-MOS T1 is set at a value which is considerably smaller than the resistance value of the built-in resistance R, a combined built-in resistance value (a combined resistance value of the built-in resistance R and an internal resistor of the P-MOS T1) is hardly affected. |
