| 摘要 |
A read only memory comprises a P-type substrate and a plurality of N+-type diffusion layers arranged checkerwise on one major surface of the substrate in which four N+-type diffusion layers having contacts are located at corners of an imaginary rectangle, and a fifth N+-type region having a contact is formed substantially at the center of the imaginary rectangle. Between the fifth N+-type diffusion layer and the first to fourth N+-type diffusion layers four MOS transistors are formed for the single contact. Gate lines are provided, each extending between adjacent two N+-type diffusion layers without overlapping them. Each of the four N+-type diffusion layers also acts as a central N+-type region of another imaginary rectangle adjacent to the first mentioned imaginary rectangle. |
