Compact mask programmable rom

Abstract

A compact mask programmable read-only memory (Mask ROM) is described, comprising a plurality of word lines, a plurality of bit lines, and a plurality of MOS-type and diffusion-type memory cells arranged in an array. The memory cells in one column are coupled to one bit line, and the gates of the MOS-type cells in one row are coupled to one word line via contacts, wherein two columns of memory cells share a column of contacts. A MOS-type cell shares its source and drain with two memory cells in the same column, and a diffusion-type cell directly connects with the diffusions of two adjacent memory cells. A constant number of continuous memory cells are grouped as a memory string, wherein the two diffusions of the two terminal memory cells are electrically connected to a bank select transistor and a ground line, respectively.