Trench isolation structure having a trench formed in a LOCOS structure and a channel stop region on the sidewalls of the trench

An isolation structure formed in a semiconductor layer between first and second active regions in order to electrically isolate the first and second active regions one from the other, the semiconductor layer comprising an outer surface, the isolation structure comprising:

• a LOCOS structure formed on the outer surface, said LOCOS structure comprising a first bird's beak structure disposed laterally adjacent the first active region and a second bird's beak structure disposed laterally adjacent the second active region;
• a trench plug disposed in a trench formed through said LOCOS structure between said first and second bird's beak structures and in said semiconductor layer, said trench comprising sidewalls defining an interface between said trench plug and the semiconductor layer;
• and
• a channel stop implantation region formed in the semiconductor layer adjacent said sidewalls of said trench, the semiconductor layer comprising silicon having a predetermined conductivity type and wherein said channel stop region comprises impurities corresponding to said first predetermined conductivity type, said LOCOS structure and said trench plug comprising silicon dioxide.