We have developed four-leg-supported superconducting Ti transition-edge sensors (TES) formed by KOH wet etching. Energy relaxation mechanism is changed from electron-phonon coupling to diffusive phonon after wet etching. The current-voltage curves of the same TES device were measured before and after wet etching. After wet etching, its thermal conductance (G) is reduced to 500pW/K from 8950pW/K. The measured effective response time ((eff)) is 143s, about 30 times larger. In addition, we have studied the optical noise equivalent power (NEP) with a cryogenic blackbody in combination with metal-mesh filters to define the radiation bandwidth. The obtained optical NEP is 5x10(-16)W/Hz, which is suitable for ground-based astronomical applications.