Method and structure for isolating semiconductor devices after transistor formation

A semiconductor structure, comprising:

• a semiconductor substrate, wherein an upper region of said semiconductor substrate includes a trench-shaped region;
• a first and a second source/drain region of a first and a second transistor respectively in said upper region of said semiconductor substrate, wherein said first and second source/drain regions include a first concentration of a first impurity;
• and
• a single layer contiguous dielectric filling said trench-shaped region and covering a first and a second gate conductor of said first and second transistors respectively;
• wherein said trench-shaped region is laterally displaced between said first and second source/drain regions, said trench-shaped region extending from an upper surface of said semiconductor substrate to a trench floor at a depth lower than said first and second source/drain regions below the upper surface of said semiconductor substrate.

A semiconductor structure, comprising:

• a semiconductor substrate, wherein an upper region of said semiconductor substrate includes a trench-shaped region;
• a first and a second source/drain region of a first and a second transistor respectively in said upper region of said semiconductor substrate, wherein said first and second source/drain regions include a first concentration of a first impurity;
• and
• a trench dielectric filling said trench-shaped region, wherein said trench dielectric is formed after said first and second source/drain regions are formed so that an upper region of said trench dielectric is free of said first impurity;
• wherein said trench-shaped region is laterally displaced between said first and second source/drain regions, said trench-shaped region extended from an upper surface of said semiconductor substrate to a trench floor at a depth lower than said first and second source/drain regions below the upper surface of said semiconductor substrate.