A method for producing a conductive nitride semiconductor substrate circuit includes the steps of forming, on an underlying substrate, a mask including dot or stripe masking portions having a width or diameter of 10 to 100 μm and arranged at a spacing of 250 to 10,000 μm; growing a nitride semiconductor crystal on the underlying substrate by hydride vapor phase epitaxy (HVPE) at a growth temperature of 1,040° C. to 1,150° C. by supplying a group III source gas, a group V source gas, and a silicon-containing gas in a V/III ratio of 1 to 10; and removing the underlying substrate, thus forming a free-standing conductive nitride semiconductor crystal substrate having a resistivity r of 0.0015 Ωcm≦r≦0.01 Ωcm, a thickness of 100 μm or more, and a radius of bow curvature U of 3.5 m≦U≦8 m.