In a method for manufacturing an optical waveguide, a core layer is formed
on a clad layer, and a stepped portion in formed in the core layer. Then,
a planar layer is formed on the core layer so that the planar layer
completely covers the stepped portion of the core layer. Finally, the
planar layer and the core layer are etched, so that the planar layer is
completely removed and the core layer is converted into a tapered core
layer.
