MANUFACTURE OF WAVEGUIDE

PURPOSE:To manufacture the precise waveguide of high quality which has small waveguide loss by forming a core layer and a clad layer by oxidizing silicon and reducing the mixture of impurities such as a hydrogen group which deteriorates the waveguide, and making the controllability of the waveguide pattern formation in a 1st process extremely excellent. CONSTITUTION:Crystal is grown on a silicon substrate 110 by expitaxial growth. This doped layer 310a is doped with phosphorus as impurities for increasing the refractive index of silicon oxide. Photoresist 150 is formed so that a specific pattern is left, and used as a mask to etch a core layer 330, forming the waveguide pattern. The substrate 110 is oxidized in a (O2+H2O) atmosphere to form the core layer 330 doped with the impurities and the clad layer 320 containing no impurity. The etching mask layer 140 is removed.