A loadless 4T SRAM powered by gate leakage current with a high tolerance for fluctuations in device parameters

Abstract

A novel loadless four-transistor static random access memory (4T SRAM) cell is proposed that consists of two N-type driver MOSFETs and two P-type access ones whose gate leakage currents from word-line are used for holding data in the cell. It is shown that the proposed cell has a higher tolerance for manufacturing device fluctuations compared with the conventional loadless 4T SRAM. Furthermore, it is free from bit-line disturb in contrast to the conventional cell. It is confirmed by simulation in 32 nm technology node that the read static noise margin (SNM) of the proposed cell reaches 138.7% of the six-transistor SRAM cell and that the hold SNM can be acceptable when the gate insulator thickness of the P-type access MOSFETs is made thinner than the N-type driver MOSFETs. The retention current for the proposed cell decreases to 66.7% of the 6TSRAM and the data rate in read increases to 125%.