<p>We demonstrate that standard wafer fabrication can produce free-standing, mechanically stable, doubly-curved 3D structures with prescribed Gaussian curvature — a capability not previously achieved through semiconductor manufacturing. The stability of the deployed structures is realized through the bistable nature of their constituent auxetic unit cells. To impose prescribed Gaussian curvatures through deployment, we conformally flatten the target 3D mesh onto the 2D plane and locally tune the microstructure of each unit cell such that its second stable equilibrium occurs at the required isotropic expansion. The resulting precursor features a spatially heterogeneous tessellation. This generative method is validated on a spherical cap deployed from a flat disk through indentation, with deployment accuracy and structural stability confirmed numerically and experimentally. The method is further applied to a range of complex 3D shapes with both positive and negative curvatures. As a functional demonstration, paraboloidal reflectors with tunable focal lengths are fabricated and deployed, with reflected patterns agreeing with geometric optics predictions. This work establishes a route from flexible electronics towards deployable electronics, broadening the spectrum of realizable 3D semiconductor devices.</p>