According to the present invention, a light-emitting semiconductor device has light-emitting elements separated by isolation trenches, preferably on two sides of each light-emitting element. The device may be fabricated by forming a single band-shaped diffusion region, then forming trenches that divide the diffusion region into multiple regions, or by forming individual diffusion regions and then forming trenches between them. The trenches prevent overlap between adjacent light-emitting elements, regardless of their junction depth, enabling a high-density array to be fabricated while maintaining adequate junction depth.