Semiconductor device having nonvolatile memory cell and field effect transistor

A method of manufacturing a semiconductor device in which a nonvolatile memory cell with a floating gate electrode and a field effect transistor are formed on a semiconductor substrate, comprising:

• (a) the first step of forming the field effect transistor, and a first conductive layer patterned into a predetermined shape via a tunnel insulating film on the semiconductor substrate;
• (b) the second step of forming a first interlevel insulating film on the semiconductor substrate so as to cover the first conductive layer and the field effect transistor;
• (c) the third step of selectively etching the first interlevel insulating film to form a first opening for exposing a surface of the first conductive layer, wherein a width of the first opening exceeds a width of the first conductive layer;
• (d) the fourth step of forming a structure made up of a second conductive layer which is formed on the first conductive layer inside the first opening and patterned into a predetermined shape, and an internal insulating film which is formed on the second conductive layer and patterned into a predetermined shape;
• and
• (e) the fifth step of forming a control gate electrode of the nonvolatile memory cell on the internal insulating film,
• wherein the first and the second conductive layers constitute the floating gate electrode, and the first conductive layer has a planar shape which can be patterned at the same time as a gate electrode of the field effect transistor.