Read only memory(rom) cell, program method of rom cell, layout method of rom cell, and rom device comprising rom cell

Abstract

A read only memory (ROM) cell, a method for programming a ROM cell, a method for forming a layout of a ROM cell, and a ROM device including ROM cells are disclosed. The ROM cell includes a gate connected to a word line, a drain (or a source) connected to a bit line, and a source (or a drain) connected to a ground voltage line, a first selection signal line or a second selection signal line, or having no connection with the first and second selection signal lines, wherein the ROM cell is programmed with data “00” by connecting the source (or the drain) to the ground voltage line, with data “10” by connecting the source (or the drain) to the first selection signal line, with data “01” by connecting the source (or the drain) to the second seletion signal line and data “11” by not connecting the source (or the drain) to any signal lines. The ROM cell can store two bits of data, and the ROM cell can decrease layout size since an additional circuit is not needed to decrease difference of parasitic capacitances between bit lines.