SEMICONDUCTOR MEMORY AND ITS MANUFACTURE

摘要

PROBLEM TO BE SOLVED: To provide a semiconductor memory which is formed on a SOI substrate and has a capacitor having a large capacitance in a buried oxide film layer under a source region. SOLUTION: A buried oxide film layer 2 is formed on a semiconductor substrate 1. A MOS transistor 4 is formed on a silicon layer 3 on the buried oxide film layer 2. A trench-type capacitor 10 is formed in the buried oxide film layer 2 and right under a source region 6 of the transistor 4. The capacitor 10 comprises a conductive capacitor electrode 11a which is buried along the inner sides so that it may be directly connected to the lower part of the source region 6, a dielectric film 12 deposited inside the capacitor electrode 11a and a capacitor electrode 11b buried through the capacitor dielectric film 12. With this structure, the area of the capacitor electrode is larger than that of a conventional device and the capacitance of the capacitor is accordingly larger.