VARIABLE CAPACITANCE DEVICE

Variable capacitance device consisting of a semiconductor substrate having a first conductivity type semiconductor layer, at least one second conductivity type semiconductor region formed in a surface portion of said first conductivity type semiconductor layer, and a barrier for generating a depletion layer formed on the surface opposite to said surface portion of said first conductivity type semiconductor layer, in which a capacitance reading-out section is disposed on said at least one second conductivity type semiconductor region. A depletion layer control section is disposed on said surface opposite to said surface portion; and said depletion layer control section is reversely biased so that said depletion layer extends from said barrier to a junction portion between said first conductivity type semiconductor layer and said at least one second conductivity type semiconductor region, whereby a capacitance variation results at said capacitance reading-out section in response to variation of the reverse bias voltage.