A method to form electronic device fins in one or more chambers that have a vacuum sealed environment, the method comprising: etching away a thickness of a substrate between first top surface areas of a substrate of a first single crystal material to form wide electronic device fins under the first top surface areas and to form trenches (105, 106) between the first top surface areas, the wide electronic device fins having wide single crystal top surfaces and wide sidewalls; forming a first thickness of a trench oxide material in the trenches and below the first top surface areas; etching a thickness of the wide single crystal top surfaces and the wide sidewalls of the wide electronic device fins to form narrower electronic device fins (507, 508, 510) from the wide fins, the narrower electronic device fins having narrower single crystal top surfaces and narrower sidewalls with a same single crystal lattice as the wide single crystal top surfaces and the wide sidewalls, wherein etching the thickness of the wide single crystal top surfaces and the wide sidewalls includes removing a thickness of between a 1 nm and 15 nm of the wide single crystal top surfaces and the wide sidewalls, said etching comprising etching using thermal processing, wherein the thermal processing includes using HCl or Cl 2 gas streams in a hydrogen environment at temperatures below 900°C or 700°C, respectively; and after etching the thickness of the wide single crystal top surfaces and the wide sidewalls, without an air break of a chamber, depositing a second single crystal material on the thinned top surfaces and thinned sidewalls to form clad electronic device fins, wherein the second single crystal material has a lattice spacing that is larger than a lattice spacing of the first single crystal material. etching away a thickness of a substrate between first top surface areas of a substrate of a first single crystal material to form wide electronic device fins under the first top surface areas and to form trenches (105, 106) between the first top surface areas, the wide electronic device fins having wide single crystal top surfaces and wide sidewalls; forming a first thickness of a trench oxide material in the trenches and below the first top surface areas; etching a thickness of the wide single crystal top surfaces and the wide sidewalls of the wide electronic device fins to form narrower electronic device fins (507, 508, 510) from the wide fins, the narrower electronic device fins having narrower single crystal top surfaces and narrower sidewalls with a same single crystal lattice as the wide single crystal top surfaces and the wide sidewalls, wherein etching the thickness of the wide single crystal top surfaces and the wide sidewalls includes removing a thickness of between a 1 nm and 15 nm of the wide single crystal top surfaces and the wide sidewalls, said etching comprising etching using thermal processing, wherein the thermal processing includes using HCl or Cl 2 gas streams in a hydrogen environment at temperatures below 900°C or 700°C, respectively; and after etching the thickness of the wide single crystal top surfaces and the wide sidewalls, without an air break of a chamber, depositing a second single crystal material on the thinned top surfaces and thinned sidewalls to form clad electronic device fins, wherein the second single crystal material has a lattice spacing that is larger than a lattice spacing of the first single crystal material.