| 摘要 |
PURPOSE:To obtain a vari-cap with little floating capacity by nullifyig or reducing to the least the lateral protrusion of an inverse-continuity-type region when a diffusion region of equal electroform and of high density is provided within a semiconductor layer of low impurity density and the shallow inverse-continuity-type region is formed there. CONSTITUTION:An n<-> type layer 2 is made to grow epitaxially on an n<+> type Si substrate 1, the whole surface is covered with an SiO2 film 3 and an window having a prescribed angle is opened by photoetching of the film 3. Next, donor impurity ions of P or As or the like are struck therein and thereby an n<+> type region 4 is formed in the layer 2. On the occasion, the ions are struck not only in the surface of the region 4 but also in the lateral surface of the film 3, whereby a damage layer 7 is to be formed. Thus, by utilizing the high etching speed of the damage layer 7, the layer 7 is removed rapidly by using a nonacid etching liquid and thereby the expansion of the window is reduced as much as possible. After that, B diffusion is performed with the film 3' after etching being left as it is and thus the shallow p<+> region 6' with little amount of protrusion outside the region 4 is obtained as a varistor with little floating capacity. |
