| 摘要 |
PURPOSE:To contribute to the enhancement of circuit integration by a method wherein a thick insulating film is formed on the bottom of an isolating trench and a thin insulating film is formed on the trench side walls. CONSTITUTION:A semiconductor substrate 1 is provided with a trench 3 covered by a thick insulating film 5. A resist 6 is applied to the semiconductor substrate 1, filling up the trench 3. A directional energy beam such as a soft X-ray beam R is projected into the trench, from a direction a prescribed angle inclined from the normal line of the semiconductor substrate 1. A portion of the resist 6 positioned on the bottom of the trench 3 remains not exposed to the beam R with the sidewalls serving as shades. The resist 6 is retained therefore only on the bottom of the trench 3 after development. The resist 6 serves as a mask in a selective etching process wherein the thick insulating film 5 is removed from the side walls of the trench 3. But the film 5 is retained on the bottom. A thin insulating film 8 is formed on the thus-exposed side walls of the trench 3. In this way, the bottom of the trench 3 is covered by a thick insulating film 50 while the side walls thereof are covered by a thin insulating film 8. This design contributes to the enhancement of circuit integration. |
