YBa2Cu3O7-x superconductor thin films were deposited on LaAlO3(100) single crystal substrates using a metalorganic chemical vapor deposition method. These films showed a critical temperature of about 90 K and a critical current density of over 105 A/cm2 at 77 K. These films showed granular structure with 0.5–1.5 μm grains. Bridge‐type junctions, 6 μm in width and 6 μm in length, were fabricated using photolithography and Ar ion milling techniques. Current‐voltage (I‐V) characteristics of these junctions with microwave irradiation at 77 K were studied. The critical current densities decreased as the irradiated microwave power increased. When microwaves are irradiated on the bridge at 77 K, the I‐V characteristics showed constant voltage steps (Shapiro steps) at ΔV=nhν/2e, but subharmonic steps. © 1995 American Institute of Physics.