Selective epitaxial formation of semiconductive films

A method of selectively forming epitaxial semiconductor material, comprising:

• providing a substrate with insulating regions and semiconductor windows formed therein;
• blanket depositing non-epitaxial silicon-containing semiconductor material over the insulating regions and epitaxial silicon-containing semiconductor material over the semiconductor windows by flowing a carbon source vapor with trisilane over the substrate wherein the silicon-containing semiconductor material comprises carbon-doped silicon, and wherein the silicon-containing semiconductor material over the semiconductor windows comprises at least about 1.0% substitutional carbon as-deposited;
• selectively etching the non-epitaxial, non-single-crystal, silicon-containing semiconductor material from over the insulating regions while leaving at least some epitaxial silicon-containing semiconductor material in the semiconductor windows by exposing the substrate to a halide gas source and a germanium source, wherein the germanium source comprises a germanium etch catalyst;
• repeating blanket depositing and selectively removing in a plurality of cycles;
• and
• wherein blanket depositing and selectively removing produces a net growth rate of the silicon-containing material of between about 4 nm/min and 11 nm/min,
• wherein in each depositing step, a thickness ratio of non-epitaxial semiconductor material over the insulating regions to the epitaxial silicon-containing semiconductor material over the semiconductor windows is less than about 1.6:1.