| 摘要 |
PURPOSE:To prevent a thermal oxide film of a part formed on the upper edge of a groove from dielectric breakdown by forming the groove formed with an upper edge with a higher surface concentration impurity diffused layer than an inner wall face on a semiconductor substrate. CONSTITUTION:An opening 4 is formed on a P-type silicon substrate 1. With a CVD-SiO2 film 3 as a mask an N type impurity, such as As, P or the like is so ion implanted to the substrate 1 as to become 1mu10<20> cm<-3> in surface concentration, and further annealed. Thus, a high concentration N-type impurity diffused layer 5 is formed. A groove 6 of the same width as that of the opening 4 is formed on the substrate 1. In this case, the diffused layer 5 remains on the upper edge of the groove 6. The films 3 and a thermal oxide film 2a are removed by RIE. Then, since the layer 5 formed on the upper edge of the groove 6 has higher concentration than that of an N-type impurity diffused layer 7 of the periphery, the thickness of a capacitor oxide film 8a by thermal oxidation is formed the same as that of a capacitor oxide film formed on the layer 7. Accordingly, the deterioration of a gate dielectric strength due to the formation of the film 8a thinner than that of the oxide film at the periphery can be eliminated. |
