A vertical optical modulator comprising: a first semiconductor layer of a first
conductivity type; a second semiconductor layer of a second conductivity type bonded
to the first semiconductor layer; a third semiconductor layer of the second conductivity
type; a dielectric layer formed between the second semiconductor layer and the
third semiconductor layer; an antenna electrode having a plurality of conductive
pieces which are formed within the dielectric layer so as to have a net-like shape
as a whole, to be separated from one another at the intersections of the net-like
shape, and to be in contact with both the second semiconductor layer and the third
semiconductor layer; a first electrode electrically connected to the first semiconductor
layer; and a second electrode electrically connected to the third semiconductor layer.
