| 摘要 |
PURPOSE:To form a thermal oxide film thickly in a short time by using a simple process by selectively bringing only the silicon-substrate concentration of the surface of an isolation region to high concentration and utilizing the concentration dependency of the velocity of oxidation. CONSTITUTION:The surfce of a P type silicon substrate 6 in 1X10<15>cm<-3> substrate concentration is oxidized to form an oxide film 7, and a nitride film 8 is deposited. A high-concentration impurity region 9 is formed, the nitride film 8 and the oxide film 7 are removed, and grooves 10 in approximately 3mum depth are formed to the silicon substrate 6 approximately vertically. Boron ions are implanted in the quantity of a dose of 50KeV, 1X10<14>atom/cm<2>, and an oxide film 14 in approximately 1mum is formed to the surface of an isolation region through thermal oxidation at 1,000 deg.C. In this case, time can be made shorter than conventional methods by approximately one fourth, and the width of an active region can be reduced to approximately one fifth. |
