Nonvolatile semiconductor memory with stable characteristic

摘要

A nonvolatile semiconductor memory device includes a substrate of a first conductive type, a plurality of stripe-shaped STI (shallow Trench Isolation) films, a plurality of control gates as word lines and a plurality of diffusion layers. The plurality of stripe-shaped STI (shallow Trench Isolation) films are formed in a surface of the substrate to extend in a column direction. The plurality of control gates are formed on the surface of the substrate to extend in a row direction. The plurality of diffusion layers are of a second conductive type and are formed in the surface of the substrate in a region between every two of the plurality of STI films and between every two of the plurality of control gates. A memory cell includes two of the plurality of diffusion layers adjacent in the column direction; and a portion of one of the plurality of control gates between adjacent two of the plurality of STI films corresponding to the adjacent two diffusion layers. The memory cell stores data of two or more bits.