A method of forming a nanowire channel on a silicon substrate using a sacrificial sub-fin layer, comprising: epitaxially growing from a first and a second substrate inner sidewall (118, 119), a sub-fin buffer layer of fin sacrificial material in a trench formed between shallow trench isolation regions (107, 108), the silicon substrate having a first and a second substrate region having the first and the second substrate inner sidewalls (118, 119) of substrate material at an angle, defining a lower trench and having a <111> crystal index, the lower trench having a lower trench upper opening; epitaxially growing from the sacrificial material a second height of a fin channel layer of fin channel material in the trench; selectively etching the STI regions to remove a height of the STI regions and to expose a first height of the sacrificial sub-fin material that can be etched above top surfaces (116, 117) of the etched STI regions; selectively etching to remove the first height of the sub-fin buffer layer of fin sacrificial material from below the fin channel layer, but leave the second height of the fin channel layer of fin channel material, to form a nanowire of the fin channel layer of fin channel material above the trench; and forming a layer of gate dielectric or buffer material on four exposed surfaces (152, 153, 235, 214) of the nanowire, wherein forming the sub-fin buffer layer of fin sacrificial material includes: epitaxially growing a first buffer layer of a first material from the first and second substrate inner sidewalls, into a portion of the height of the upper trench; and epitaxially growing a second buffer layer of a second material from a top surface of the first buffer layer and extending the first height above the top surfaces of the STI regions. wherein forming the fin channel layer of fin channel material includes: epitaxially growing a first channel layer of the first material from a top surface of the second buffer layer; epitaxially growing a second channel layer of the second material from a top surface of the first channel layer; and epitaxially growing a third channel layer of the first material from a top surface of the second channel layer. epitaxially growing from a first and a second substrate inner sidewall (118, 119), a sub-fin buffer layer of fin sacrificial material in a trench formed between shallow trench isolation regions (107, 108), the silicon substrate having a first and a second substrate region having the first and the second substrate inner sidewalls (118, 119) of substrate material at an angle, defining a lower trench and having a <111> crystal index, the lower trench having a lower trench upper opening; epitaxially growing from the sacrificial material a second height of a fin channel layer of fin channel material in the trench; selectively etching the STI regions to remove a height of the STI regions and to expose a first height of the sacrificial sub-fin material that can be etched above top surfaces (116, 117) of the etched STI regions; selectively etching to remove the first height of the sub-fin buffer layer of fin sacrificial material from below the fin channel layer, but leave the second height of the fin channel layer of fin channel material, to form a nanowire of the fin channel layer of fin channel material above the trench; and forming a layer of gate dielectric or buffer material on four exposed surfaces (152, 153, 235, 214) of the nanowire, wherein forming the sub-fin buffer layer of fin sacrificial material includes: epitaxially growing a first buffer layer of a first material from the first and second substrate inner sidewalls, into a portion of the height of the upper trench; and epitaxially growing a second buffer layer of a second material from a top surface of the first buffer layer and extending the first height above the top surfaces of the STI regions. wherein forming the fin channel layer of fin channel material includes: epitaxially growing a first channel layer of the first material from a top surface of the second buffer layer; epitaxially growing a second channel layer of the second material from a top surface of the first channel layer; and epitaxially growing a third channel layer of the first material from a top surface of the second channel layer. epitaxially growing a first buffer layer of a first material from the first and second substrate inner sidewalls, into a portion of the height of the upper trench; and epitaxially growing a second buffer layer of a second material from a top surface of the first buffer layer and extending the first height above the top surfaces of the STI regions. wherein forming the fin channel layer of fin channel material includes: epitaxially growing a first channel layer of the first material from a top surface of the second buffer layer; epitaxially growing a second channel layer of the second material from a top surface of the first channel layer; and epitaxially growing a third channel layer of the first material from a top surface of the second channel layer. epitaxially growing a first channel layer of the first material from a top surface of the second buffer layer; epitaxially growing a second channel layer of the second material from a top surface of the first channel layer; and epitaxially growing a third channel layer of the first material from a top surface of the second channel layer.