METHOD FOR FABRICATING SEMICONDUCTOR DEVICE

摘要

PURPOSE: A method for fabricating a semiconductor device is to prevent impurity ions in channel formation region within semiconductor substrate from being out-diffused during a subsequent thermal annealing. CONSTITUTION: A method for fabricating a semiconductor device comprises the steps of: etching a semiconductor substrate(11) to define a trench(12A,12B,12C) having a predetermined depth from the surface of the substrate; forming a nitride-treated oxide layer(14) on the substrate including the trench by thermally annealing the substrate in an ambient of NO or N2O. The nitride-treated oxide layer is formed by forming an oxide layer on the whole surface of the semiconductor substrate including the trench and thermally annealing the resultant semiconductor substrate in an ambient of NO or N2O. The nitride-treated oxide can also be formed by implanting nitrogen ions into the oxide layer with a tilt angle.