Yoshikazu Ohno

An experimental 256-Mb DRAM with boosted sense-ground scheme

In developing the 256-Mb DRAM, the data retention characteristics must inevitably be improved. In order for DRAMs to remain the semiconductor device with the largest production volume in the 256-Mb era, we must develop a cost effective device with a small chip size and a large process tolerance. In this paper, we propose the BSG (boosted sense-ground) scheme for data retention and FOGOS (folded global and open segment bit-line) structure for chip size reduction. We have fabricated an experimental 256-Mb DRAM with these technologies and obtained a chip size of 304 mm/sup 2/ and a performance of 34 ns access time. >

A 34-ns 16-Mb DRAM with controllable voltage down-converter

A high-speed 16-Mb DRAM with high reliability is reported. A multidivided column address decoding scheme and a fully embedded sense-amplifier driving scheme were used to meet the requirements for high speed. A low-power hybrid internal power supply voltage converter with an accelerated life-test function is also proposed and was demonstrated. A novel substrate engineering technology, a retrograded well structure formed by a megaelectronvolt ion-implantation process, provides a simple process sequence and high reliability in terms of soft error and latch-up immunity. >