To provide a semiconductor device which has a structure capable of easily processing the end shape of a gate electrode including an isolation region between gate electrodes, and to provide a manufacturing method thereof.

In the semiconductor device, first and second semiconductor regions 12 and 13 having first and second formation regions on a semiconductor substrate are sectioned respectively by an element isolation insulating film 11 having a top surface above a top surface of the semiconductor substrate 10, a gate insulating film 14 and first and second gate electrodes G1 and G2 are formed on the first and second channel formation regions, and source drain regions are formed at surface layer portions of the first and second semiconductor regions on both sides thereof. The first and second gate electrodes are nearly as tall as the element isolation insulating film in the first and second semiconductor regions, and also have a first conductive layer 15p formed having its end in contact with a side surface of the element isolation insulating film and a second conductive layer 16s formed, on the first conductive layer, projecting from the end onto the element isolation insulating film.