Method of making a mask ROM using tunnel current detection to store data

摘要

Each of the portions corresponding to the crossings of a plurality of first strip conductive layers serving as bit lines and a plurality of second strip conductive layers serving as word lines crossing the conductive layers at right angles is used as one memory cell. An oxide film is provided between the first strip conductive layers and the second strip conductive layers. The thickness of this oxide film is set in each memory cell according to stored data. Also a multi-value memory can be realized, since the amount of stored data in each memory cell is an arbitrary amount of 1 bit or more by making the stored data of a plurality of types of memory cells having different thicknesses in the tunnel oxide film 15 correspond to a plurality of different data. The size of each memory cell can be reduced since the occupying area of each memory cell on the semiconductor substrate is dependent on the width of the first strip conductive layer and the second strip conductive layer. An insulation film in which tunnel phenomenon is generated can be formed using conventional manufacturing technology.