MEMORY DEVICE HAVING PEDESTAL COLLAR STRUCTURE FOR CHARGE-HOLDING IMPROVEMENT OF TRENCH-TYPE DRAM CELL AND FORMING METHOD THEREOF

摘要

PROBLEM TO BE SOLVED: To provide a structure and a method for a trench-type capacitor improved in its charge holding capability. SOLUTION: The memory device includes a trench 23 which is formed on a substrate and has an upper part. A collar oxide film 21 is arranged at the upper part of the trench. A collar oxide film includes a pedestal 25. A conductor is charged in the trench. The pedestal reduces a leak of charges in the conductor. The method for forming the memory device, having the collar oxide film having the pedestal collar, is also disclosed.