Varactor diode controllable by surface layout design

Abstract

An area-variable varactor diode is disclosed, in which the capacitance can be arbitrarily varied under an applied bias voltage. The area-variable varactor diode is characterized in that, in order to ensure freedom to designing the epi-layer, to obtain the desired capacitance characteristics, and to facilitate the integration with other elements, a steeply varied depletion layer area is provided through a variation of the surface layout area, and thus, varied capacitance characteristics are obtained. In steeply varying the area of the depletion layer, an etching of the active layer, a selective epi-layer growth, and an ion implantation are carried out or a combination of them is carried out. The capacitance characteristics are varied in accordance with the pattern of the mask, and therefore, a restriction is not imposed on the epi-layer, with the result that an integration with other elements becomes easy. Further, because the mask pattern is resorted to, it becomes possible to manufacture a varactor diode which shows a capacitance variation of a strong non-linearity and a large capacitance variation rate.