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 DRAM's 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 mm² and a performance of 34 ns access time