Memory cell of type permanent static random-access memory (SRAM), comprises two interconnected inverter circuits and transistors for programming by degradation of gate oxide layers

摘要

The memory cell (10) comprises two inverter circuits (14,16) interconnected between the data nodes (N1,N2) so to form a memory circuit (12), two programming transistors (28,30) for implementing an irreversible degradation of the gate oxide layers of transistors (18,18'), and two transistors (32,34) for implementing the functioning of the memory cell after programming. Each inverter circuit (14,16) comprises supplementary MOS transistors (18,20;18',20') connected in series between a supply voltage source (VDD) and the ground circuit (22). Each inverter circuit comprises a p-MOS transistor (18,18') and an n-MOS transistor (20,20'), and the data nodes (N1,N2) are formed between the two transistors, n-MOS and p-MOS. The degraded MOS transistor is a transistor with thin gate oxide layer (GO1). The oxide layer is degraded at least locally so to obtain a variation of current through the transistor at the time of reading the cell. The programming transistors (28,30), or the diodes, are connected between the programming control line (PROG) and the transistors of the inverter circuits. The n-MOS programming transistors (28,30) ensure a selective connection of the gates of the transistors (18,18') to a programming voltage (VREF) at a level sufficient to cause the degradation of the gate oxide layers of the transistors. The inverter circuits are interconnected by the intermediary of a n-MOS transistor (32,34) connected to the control line (SRAM) of functioning the cell as the SRAM cell. The drain and the source electrodes of the transistors (32,34) are connected to the gates of the transistors of the inverter circuits.