| 摘要 |
PURPOSE:To highly integrate a semiconductor memory without decreasing its reliability by stepwisely forming a sidewall opposed to the capacitor electrode of an insular semiconductor region. CONSTITUTION:Grooves are dug by RIE on the element separating region of a P-type Si substrate 1, and a plurality of insular semiconductor regions of rectangular pattern having a stepwise sidewall 2 are formed. Since an MOS capacitor is formed by utilizing parts of three stepwise sidewalls and upper surface of the ends of the insular region, a large capacitor capacity can be performed with smaller occupying area than the conventional structure which utilizes only vertical wall. The separation between the capacitors of the adjacent memory cell is effectively achieved by an insulating film 32 buried in the deepest portion of the groove and a P<+> type layer 4 disposed under the groove, and a punch-through hardly occurs as compared with the deeper groove from the boundary of the substrate of the element separating region in the capacitor region. Accordingly, a highly integrated (d) RAM having high reliability can be obtained. |
