An optimized waveguide taper structure is investigated for the efficient spot-size transformation of guided waves on InP-based optoelectronically integrated circuits. The simple two-layer structure is suitable for very low-loss chip-fiber interconnections. Using a special layout and process steps, the earlier strong requirements on lithographic resolution can be reduced to values of 200-300 nm, maintaining, however, the low-loss transformation properties. The quality of different process sequences are compared with respect to their loss properties.