| 摘要 |
PURPOSE:To enable to separate wells via ultrafine region and to form an ultrafine well by filling insulator by forming in advance grooves, and then diffusing the well. CONSTITUTION:An SiO2 film 102 and an Si3N4 film 103 are accumulated on an N type Si substrate 101, and sequentially etched to form deep grooves. An SiO2 film 105 is accumulated on the overall surface, a photoresist 106 is coated, etched back to remove parts of the films 106, 105, the SiO2 is buried in the grooves, and with the Si3N4 film 103' as a mask selective oxidation is performed. Part of the film 103' is removed by etching, boron ions are implanted to form a P type region 106. A wafer is heat treated, boron is diffused, and a P- well 107 is formed. A thermally oxidized film 108 is formed during this step. When the films 102, 108 are etched and removed, a wafer formed with P-well 107 is formed. According to this method, a well isolating oxidized film 105 and the well 197 are self-aligned and formed, and lateral diffusion is eliminated to obtain ultrafine well and element isolating region. |
