| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor device containing a nonvolatile memory transistor having split gate structure and a method of fabrication in which the speed of write operation or read operation can be controlled. SOLUTION: The method for fabricating a semiconductor device having a nonvolatile memory transistor comprises step (a) for forming a gate insulation layer 20 on a semiconductor substrate 10, step (b) for forming a floating gate 22 on the gate insulation layer 20, step (c) for depositing a second insulation layer 50 on the semiconductor substrate 10, step (d) for etching the second insulation layer 50 entirely to form an intermediate insulation layer 26 having a specified film thickness distribution and touching at least a part of the floating gate 22 to function as a tunnel insulation layer, step (e) for forming a control gate 28 on the intermediate insulation layer 26, and step (f) for forming impurity diffusion layers 14, 16 constituting a source region and a drain region in the semiconductor substrate 10.
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