| 摘要 |
PURPOSE:To allow the prevention of reduction of pattern forming region and generation of crystal strain, the improvement of the integration degree and the reduction of the deterioration of withstand voltage, by forming a polycrystalline Si layer only on the side surface of a groove after forming an etching groove, when a buried Si oxide film is formed. CONSTITUTION:B as a P type impurity is added by an ion implantation method. Thereafter, using a thermal oxidation method, a buried Si oxide film 8' is formed. When the thermal oxidation is performed at 900-1,000 deg.C by high pressure oxidation for example, an oxide film can be easily formed. The lower surface of the groove is oxidized when selective oxidation, but the Si substrate itself is not oxidized. Therefore, an Si oxide film is not formed under an Si nitride film 5. A bird head is not formed, the reduction of pattern forming region due to a selective oxidation and the generation of crystal strain can be prevented, high density formation and miniaturization can be performed, the unstability of characteristic due to strains is prevented, and, at the same time as the formation of the buried Si oxide film 8', a channel stopper 15 and the P type region 7'' a region to prevent the deterioration of withstand voltage can be formed. |
