Semiconductor structure and method of manufacture

DETAILED DESCRIPTION OF THE DRAWINGS FIGS.
1-20 are highly enlarged transparent oblique isometric views of a semiconductor structure 10 having shielding structures in which electrical devices are manufactured.
In accordance with one embodiment of the present invention, the shielding structures are comprised of localized buried layers in combination with highly doped sidewalls that are formed in a lightly doped semiconductor material, wherein the conductivity types of the buried layers, the highly doped sidewalls, and the semiconductor material are the same.
The use of localized buried layers prevents cross-talk that occurs in semiconductor circuits that share a common buried layer.
In addition, the lightly doped semiconductor material helps attenuate any noise that may be transmitted through the substrate.
In accordance with another embodiment, the buried layer is formed from a buried layer of the same conductivity type as the semiconductor material, but the sidewalls are formed from an electrically conductive material such as metal.
In accordance with yet a third embodiment, the shielding structure is formed from metal.
It should be understood that the electrical devices within the shielding structures may be bipolar transistors, Insulated Gate Field Effect Transistors (IGFET's), Junction Field Effect Transistors (JFET's), resistors, capacitors, etc.
Although specific materials, conductivity types, thicknesses, and other parameters are set forth herein, it should be understood that these are not meant to be limiting and only serve to show a preferred embodiment of the present invention.
Further, it should be understood that the same reference numerals are used in the figures to denote the same elements.
FIG.
1 is a highly enlarged cross-sectional isometric view of a semiconductor structure 10 having portions 15 and 16 at an early stage of manufacture in accordance with a first embodiment of the present invention.
In accordance with this embodiment, an IGFET is fabricated in portion 15, therefore, portion 15 is also referred to as an IGFET region