| 摘要 |
PURPOSE:To increase the quantity of charges stored by the volume of a P-N junction section in the periphery of a trench by laminating P type Si on P<+>Si and forming the trench up to the interface or a section deeper than the interface. CONSTITUTION:A P layer 10 in concentration of 1X10<14>-1X10<16>/cm<3> is superposed on a P<+> substrate 9 in impurity concentration of 1X10<16>-1X10<21>/cm<3> in approximately 3mum, and a trench in approximately 4mum depth is formed in a region isolated by an SiO2 film 2 through plasma etching. An SiO2 thin-film 3 is shaped on the whole surface, and the trench is buried by poly Si to form a trench region 8 with a flat surface. When N<+> type source and drain 6, a gate electrode 4 and a capacitance electrode 5 are shaped, poly Si in the trench has the same function as the capacitance electrode 5. Charge storage capacitance is made larger than conventional devices by capacitance by the electrode 5 and the SiO2 film 3 and capacitance shaped by an N<+> layer 12 along the film 3 and a depletion layer 11 between a P layer 10 and a P<+> layer 9, the trench section 8 is not affected even through the fining of a pattern, and a dynamic RAM stably operating even through fining is obtained. An N type substrate is also effective similarly. |
