| 摘要 |
PURPOSE:To increase the noise withstanding voltage (electrostatic withstanding voltage) of a variable electrode practically sufficiently, and to improve utility and mass productivity by selecting the junction withstanding voltage of a Pn junction connected to a capacitance electrode to a low value. CONSTITUTION:A channel cut 16 in a P+ diffusion region is formed around a substrate surface in a P well 14, and a capacitance electrode 20 is constituted by connecting the P well 14, an N type diffusion region 15 and a shield electrode 13. A distance 22 between a channel cut 17 in an N+ diffusion region surrounding the periphery of the P well 14 and the P+ channel cut 16 is adjoined within 4mum. A P type diffusion region 19 isolates an N type diffusion region 18 as a capacitance electrode from a substrate 11. A protective circuit is inserted between a variable electrode 21 lead out of the region 18 and an external terminal. |
