JPS57190352A - Programmable read only memory - Google Patents

Abstract

PURPOSE:To contrive to enhance read/write characteristic at a channel injection type programmable read only memory (PROM) by a method wherein a substrate voltage generating circuit and a control circuit for change-over of substrate voltage when read/write is to be performed are made as built-in. CONSTITUTION:Because channel length is selected as not to deteriorate the traditional write characteristic, the read speed is sacrificed ultimately. The substrate voltage generating circuit and the control circut for change-over of the substrate voltage when read/write is to be performed are made as built-in, channel length of the memory cell is shortened to improve gm, the discharging speed of electric charge of a digit line is made fast to enhance the read speed, and in regard to write, a reverse bias is applied to the substrate making the substrate voltage generating circuit to operate, and a leakage current of the memory cell is suppressed to enhance the write characteristic. At the exemplified UV-PROM, when write is performed with the reverse bias VSUB=-3V, the margin for electric power source voltage is enlarged, and when read is to be performed, the substrate voltage becomes as VSUB=0, and the high speed property can be obtained.