The invention forms an epitaxial silicon-containing layer on a silicon germanium, patterned strained silicon, or patterned thin silicon-on-insulator surface and avoids creating a rough surface upon which the epitaxial silicon-containing layer is grown. The lens includes a voltage application portion arranged on at least one of the at least three substrates. Second and third ducts extends in parallel with the first duct. The second gate layer is etched, thereby forming second gates patterned with a spacer shape on sidewalls of the first gate.