There is described a method for creating a thermally-isolated microstructure on a slab of mono-crystalline silicon which uses a hybrid dry-then-wet etch technique that when controlled, can produce microstructures without any silicon adhering underneath, microstructures having small masses of silicon adhering underneath, and microstructures that are still attached to the slab of mono-crystalline silicon via a waisted silicon body. When creating the microstructures with a waisted silicon body, the thermal isolation of the microstructure can be designed by controlling the depth of the etching and the size of the waist.