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 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.

Semiconductor structures and devices including strained material layers having impurity-free zones, and methods for fabricating same. Certain regions of the strained material layers are kept free of impurities that can interdiffuse from adjacent portions of the semiconductor. When impurities are present in certain regions of the strained material layers, there is degradation in device performance. By employing semiconductor structures and devices (e.g., field effect transistors or FETs) that have the features described, or are fabricated in accordance with the steps described, device operation is enhanced.

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.

Semiconductor structures and devices including strained material layers having impurity-free zones, and methods for fabricating same. Certain regions of the strained material layers are kept free of impurities that can interdiffuse from adjacent portions of the semiconductor. When impurities are present in certain regions of the strained material layers, there is degradation in device performance. By employing semiconductor structures and devices (e.g., field effect transistors or FETs) that have the features described, or are fabricated in accordance with the steps described, device operation is enhanced.

A semiconductor device has first wiring layers and a plurality of dummy wiring layers that are provided on the same level as the first wiring layers. The semiconductor device defines a row direction, and first virtual linear lines extending in a direction traversing the row direction. The row direction and the first virtual linear lines define an angle of 2-40 degrees, and the dummy wiring layers are disposed in a manner to be located on the first virtual linear lines. The semiconductor device also defines a column direction perpendicular to the row direction, and second virtual linear lines extending in a direction traversing the column direction. The column direction and the second virtual linear lines define an angle of 2-40 degrees, and the dummy wiring layers are disposed in a manner to be located on the second virtual linear lines.

A multilayer semiconductor device includes first wirings extending in a first direction adjacent to each other in a second direction. Dummy wirings are arranged between the first wirings and a 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 dummy wirings have a first dummy wiring, a second dummy wiring, a third dummy wiring, a fourth dummy wiring, and a fifth dummy wiring. When the dummy wirings are rotated around a center of the first dummy wiring through 90 degrees, centers of the second, third, fourth, and fifth dummy wirings are aligned with centers of the fourth, fifth, third, and second dummy wirings prior to being rotated.

Semiconductor structures and devices including strained material layers having impurity-free zones, and methods for fabricating same. Certain regions of the strained material layers are kept free of impurities that can interdiffuse from adjacent portions of the semiconductor. When impurities are present in certain regions of the strained material layers, there is degradation in device performance. By employing semiconductor structures and devices (e.g., field effect transistors or FETs) that have the features described, or are fabricated in accordance with the steps described, device operation is enhanced.

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.