Trench isolation with Del (nabla)-shaped buried oxide for 256 mega-bit DRAMs

A new trench isolation with Del -shaped buried oxide is proposed. The Del -shape of the buried oxide is a key to control trench sidewall inversion which is a well known obstacle for practical application of a trench isolation. Its fabrication process is simple and has good feasibility for 256 Mb DRAM application. In addition to good isolation characteristics, low junction capacitance is an advantage for DRAM performance.<<ETX>>