Abstract: A single stage expose/etch partial etching process fabricates at least two areas of differing remaining thicknesses in a substrate. The process comprises (a) applying a resist mask to the substrate; (b) patterning the mask in a first area with a plurality of first mask openings and first mask land features having land feature widths and spacings selected such that the first area is a critical etch space having a reduced etch factor; (c) patterning the mask in a second area having at least one second mask opening, such that the average distance between edges of the second mask opening is greater than the average critical etch space.The critical etch space is the distance between edges of a resist mask opening below which the etch factor for that distance begins to decrease.When the substrate is isotropically etched through the first and second areas of the mask for a set period of time, the etch removal rate for the first area is less than the etch removal rate for the second area.