| 摘要 |
PURPOSE:To shorten a time when the surge voltage of an electrostatic protective circuit is clamped, and to increase protective capacity against static electricity by arranging a grounded diffusion layer adjacent to a region in the vicinity of the inner pad of an electrostatic protective diffusion resistor. CONSTITUTION:The grounded N-type diffusion layer 9 is arranged additionally. When a negative surge is applied to a pad-side terminal 3, the potential of a P type substrate 5 is brought to negative one when a diode containing series equivalent resistors 6, 7 formed by the P type substrate 5 and an N type diffusion layer 6 is brought to a conductive state. Consequently, a junction formed by the P type substrate 5 and the N type diffusion layer 9 is broken down, and a current path, which passes through the P type substrate 5 from the N type diffusion layer 9 and reaches the N type diffusion layer 6, is generated. When a space between the N type diffusion layers 6 and 9 is made surfficiently smaller than the thickness of the P type substrate 5, series equivalent resistance in the P type substrate is reduced largely. Accordingly, the forward series equivalent resistance of a diode formed by the N type diffusion layer 6 and the P type substrate 5 is reduced apparently, and a time when the negative surge applied to the terminal 3 is clamped up to approximately 0.6-0.7V is shortened. |
