A control gate electrode and a memory gate electrode of a memory cell of a non-volatile memory are formed in a memory cell region of a semiconductor substrate, and a dummy gate electrode is formed in a peripheral circuit region. Then, n.sup.+-type semiconductor regions for a source or a drain of the memory cell are formed in the memory cell region and n.sup.+-type semiconductor regions for a source or a drain of MISFET are formed in the peripheral circuit region. Then, a metal silicide layer is formed over the n.sup.+-type semiconductor regions but the metal silicide layer is not formed over the control gate electrode, the memory gate electrode, and the gate electrode. Subsequently, the gate electrode is removed and replaced with the gate electrode for MISFET, Then, after removing the gate electrode and replacing it with a gate electrode for MISFET, a metal silicide layer is formed over the memory gate electrode and the control gate electrode.

A method of fabricating a MOS transistor having a thinned channel region is described. The channel region is etched following removal of a dummy gate. The source and drain regions have relatively low resistance with the process.

A control gate electrode and a memory gate electrode of a memory cell of a non-volatile memory are formed in a memory cell region of a semiconductor substrate, and a dummy gate electrode is formed in a peripheral circuit region. Then, n.sup.+-type semiconductor regions for a source or a drain of the memory cell are formed in the memory cell region and n.sup.+-type semiconductor regions for a source or a drain of MISFET are formed in the peripheral circuit region. Then, a metal silicide layer is formed over the n.sup.+-type semiconductor regions but the metal silicide layer is not formed over the control gate electrode, the memory gate electrode, and the gate electrode. Subsequently, the gate electrode is removed and replaced with the gate electrode for MISFET. Then, after removing the gate electrode and replacing it with a gate electrode for MISFET, a metal silicide layer is formed over the memory gate electrode and the control gate electrode.

A method of fabricating a MOS transistor having a thinned channel region is described. The channel region is etched following removal of a dummy gate. The source and drain regions have relatively low resistance with the process.

A multilayer semiconductor device includes first wirings extending in a first direction and arranged adjacent to each other in a second direction. Dummy wirings are arranged between the first wirings and the second wiring at crossing points between first virtual linear lines extending in a third direction and second virtual linear lines extending in a fourth direction. The third and fourth directions are neither parallel nor orthogonal to the first and second directions. The dummy wirings have a first, a second, and a third dummy wiring. Centers of the second and third dummy wirings are nearest to a center of the first dummy wiring relative to others of the dummy wirings. The respective centers of the first, second, and third dummy wirings are aligned on a third virtual linear line extending in a fifth direction neither parallel to nor perpendicular to the first and second directions.

A method of fabricating a MOS transistor having a thinned channel region is described. The channel region is etched following removal of a dummy gate. The source and drain regions have relatively low resistance with the process.

A multilayer semiconductor device includes first wirings extending in a first direction and arranged adjacent to each other in a second direction. Dummy wirings are arranged between the first wirings and the second wiring at crossing points between first virtual linear lines extending in a third direction and second virtual linear lines extending in a fourth direction. The third and fourth directions are neither parallel nor orthogonal to the first and second directions. The dummy wirings have a first, a second, and a third dummy wiring. Centers of the second and third dummy wirings are nearest to a center of the first dummy wiring relative to others of the dummy wirings. The respective centers of the first, second, and third dummy wirings are aligned on a third virtual linear line extending in a fifth direction neither parallel to nor perpendicular to the first and second directions.

A multilayer semiconductor device includes first wirings extending in a first direction and arranged adjacent to each other in a second direction. Dummy wirings are arranged between the first wirings and the second wiring at crossing points between first virtual linear lines extending in a third direction and second virtual linear lines extending in a fourth direction. The third and fourth directions are neither parallel nor orthogonal to the first and second directions. The dummy wirings have a first, a second, and a third dummy wiring. Centers of the second and third dummy wirings are nearest to a center of the first dummy wiring relative to others of the dummy wirings. The respective centers of the first, second, and third dummy wirings are aligned on a third virtual linear line extending in a fifth direction neither parallel to nor perpendicular to the first and second directions.

A method of fabricating a MOS transistor having a thinned channel region is described. The channel region is etched following removal of a dummy gate. The source and drain regions have relatively low resistance with the process.

A method of fabricating a MOS transistor having a thinned channel region is described. The channel region is etched following removal of a dummy gate. The source and drain regions have relatively low resistance with the process.