JPS6459855A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable good epitaxial growth of a silicon to be performed in the later process without a modified layer being formed, by etching a polycrystalline film using an isotropic ion etching technique during a trench formation. CONSTITUTION:After an N<+> type region 2 is formed in the part of the surface of a P-type silicon substrate 1, a silicon dioxide film 3, a polycrystalline silicon film 4 and a silicon dioxide film 5 are in turn formed on the substrate body. The two layers of the silicon dioxide 5 and the polycrystalline silicon film 4 are thereafter selectively etched using a reactive ion etching technique to form both trenches 7 and 8. In this case, the degree of the anisotropy is so weakened by increasing the pressure in the ion etching, and so forth, as to form a concave part 6 in the sidewall of each the trench. During the trenches 7 and 8 which have been formed are then filled with a single-crystal silicon 9 respectively, the crystal grain growth of the polycrystalline silicon 4 occurs in the concave part 6 of the sidewall. However, the concave part 6 is filled with the single-crystal silicon which has been grown from the substrate as a seed crystal, which prevents the polycrystalline silicon from extending from the concave part 6 into the trench.