Abstract: A method for reduction and control of the size of etched apertures and vias for integrated circuit devices. A first aperture having a horizontal dimension greater than a desired aperture dimension is etched in an insulating layer. The sidewalls and bottom surface of the first aperture are then lined with a conformal material such as ozone/TEOS or silicon nitride, and the conformal material is anistropically etched. The anisotropic etch removes the conformal material from the bottom surface, but leaves an amount of conformal material on the sidewalls to reduce the horizontal dimension to the desired aperture dimension. Where ozone/TEOS is used, the conformal layer may be formed at relatively low temperatures such as T=390.degree. C.