Semiconductor structure and method of manufacture

A method to manufacture a semiconductor structure, comprising:

• removing a portion of a semiconductor material using an orientation-dependent etch to form a first cavity that extends at least about one micron or greater below the surface of the semiconductor material, a second cavity that extends at least about one micron or greater below the surface of the semiconductor material, wherein the first cavity is isolated from the second cavity, a first protrusion comprising a portion of the semiconductor material is between the first cavity and the second cavity, and the semiconductor material comprises silicon, wherein said removing results in the first cavity or the second cavity, or combinations thereof, to have sidewalls that are formed mainly by {111} planes of silicon crystal of the semiconductor material to be perpendicular, or substantially perpendicular, to a planar surface of the semiconductor material;
• performing a thermal oxidation to convert a portion of the silicon of the semiconductor material to silicon dioxide;
• forming a first dielectric material over the first cavity, over the second cavity, over at least a portion of the semiconductor material, and over at least a portion of the first protrusion, wherein the first dielectric material extends at least partially into the first cavity and the second cavity and caps the first cavity and the second cavity to create sealed voids having a lower dielectric constant than the semiconductor material;
• and
• forming at least a portion of an electrically conductive material over at least a portion of the first dielectric material such that the sealed voids provide a reduced capacitance between the electrically conductive material and the semiconductor material.