Nonvolatile semiconductor memory device and fabrication method

Abstract

A nonvolatile semiconductor memory device and a method of fabricating the device are provided that allow the use of dry etching when removing the ONO film and that eliminate the danger of etching the silicon substrate in the gate oxide film formation areas even in the event of over-etching. In the process of fabricating a nonvolatile semiconductor memory device that is provided with a memory cell area including nonvolatile memory and a peripheral circuit area including circuits for controlling the nonvolatile memory, an insulative material that is to become an insulating film overlying floating gate electrodes is formed over the entire surface of each area and over a first conductive layer in the peripheral circuit area, and a dummy pattern is provided in the boundary areas between the memory cell area and peripheral circuit area so as to surround the memory cell area, this dummy pattern being composed of: a first conductive material that constitutes the floating gate electrodes of the nonvolatile memory, a second conductive material that constitutes the control gate electrodes of the nonvolatile memory, and an ONO film that constitutes an insulating film between the floating gate electrodes and the control gate electrodes.