PREPARATION OF SILICON SUBSTRATE

摘要

A silicon substrate is prepared by furnishing a silicon substrate (10) having a step (11) of at least 5 .mu.m high on one surface, forming by high pressure heat oxidation an oxide film (12) which is thinner than the step, and removing the oxide film on the higher surface region until the silicon surface is exposed in the higher surface region while leaving the oxide film on the lower surface region. Because of excellent electrical properties, minimized warpage, a substantially constant oxygen concentration, and a definitely ascertainable oxide-silicon boundary, the silicon substrate is suitable for use in optical waveguide devices.