A semiconductor device having a rewritable nonvolatile memory cell including a first field effect transistor for memory, a circuit including a second field effect transistor and a circuit including a third field effect transistor, the transistors each including a gate insulating film formed over a semiconductor substrate, a gate electrode over the gate insulating film and sidewall spacers over the sidewalls of the corresponding gate electrode. Sidewall spacers of the first field effect transistor are different from those of at least the second field effect transistors. Also, the gate insulating film of the third field effect transistor has a thickness larger than that of the second field effect transistor and the gate electrode of the third field effect transistor has a length different from that of either the first field effect transistor or second field effect transistor. The sidewall spacers of the first field effect transistor include a first silicon oxide film, a first silicon nitride film over the first silicon oxide film and a second silicon oxide film over the first silicon nitride film.