Eprom virtual ground array

Abstract

An electrically programmable read only memory contains alternating metal bit lines and diffused bit lines. Each diffused bit line is broken into a plurality of segments. Each of the segments of the diffused bit line comprises a virtual source. A multiplicity of floating gate transistors are arranged in rows and columns. The floating gate transistors in each column are divided into M groups of N floating gate transistors each. The floating gate transistors in the n.sup.th and the (n+1).sup.th columns, where n is an odd integer given by 1.ltoreq.n.ltoreq.N and (N+1) is the maximum number of columns in the array are connected to the segments of one diffused bit line placed between the n.sup.th and the (n+1).sup.th columns. At least one first transfer transistor is arranged to connect one segment comprising a virtual source to a first metal bit line. The first metal bit line functions as the source for the N floating gate transistors in the (n+1).sup.th column connected to said one segment. At least one second transfer transistor connects the same one segment comprising a virtual source to a second metal bit line. The second metal bit line functions as a source for the N floating gate transistors in the n.sup.th column connected to said one segment. The removal of each select transistor from the cell where it previously resided in series with its corresponding floating gate transistor, and the combining of a plurality of select transistors into one select transistor substantially reduces the area taken by each memory cell in the array.