Dielectric isolation method using shallow oxide and polycrystalline silicon utilizing a preliminary etching step

A method for achieving isolation of the silicon islands of integrated circuits comprising:

• isotropically etching to a predetermined depth those portions of a silicon substrate surface which correspond to the area surrounding the bottom of silicon islands to be subsequently grown,
• oxidizing the preceding etched silicon surface,
• simultaneously growing a polycrystalline layer of silicon on said oxidized surface and an epitaxial layer on the remaining portions of said silicon substrate to form said silicon islands,
• masking the surface of said silicon islands leaving the portions of said islands contiguous to said polysilicon surface unmasked and also any regions of said island surface for oxide isolation between impurity junctions,
• oxidizing the exposed silicons, the depth of such silicon etching and the thickness of said oxide being such that the top of said oxide is substantially co-planar with the top surface of the masked silicon islands and the bottom of the oxide extends below the junction depth of junctions to be subsequently formed in said epitaxial silicon islands,
• removing said mask on the surface of the silicon islands to provide a surface into which impurities may be provided to form junction devices in said islands.