Using a newly developed technique of shaped crystal growth from the vapor, we have obtained a lateral conformal GaAs single‐crystal growth between two Si3N4films. 0.6‐&mgr;m‐thick GaAs films of (100) surface orientation were grown over extensions of 15 &mgr;m in a standard arsenic trichloride vapor phase epitaxy reactor. The surface aspect of the films after removal of the top Si3N4layer is specular and these films are virtually dislocation‐free.