By directly heating a surface-dezincified polycrystalline brass (Cu70Zn30 alloy) in ambient conditions, semiconductor nanostructure networks composed of CuO nanofilm and ZnO nanowires have been successfully fabricated. The dezincification induced by metallographic etching on Cu70Zn30 polycrystalline alloy surface created heterogeneous networks composed of individual Cu-rich micrograin surfaces and surrounding grain boundaries. The comparative thermal oxidation investigations show distinct growth of semiconductor nanowire/nanofilm network junctions on dezincified Cu70Zn30 substrates compared to the random ZnO nanowires growth on nonetched brass substrates. The grain boundary region is mostly dominated by ZnO nanowires, while each grain surface was overgrown with CuO nanofilm, forming nanowire/nanofilm network junctions. The different growth habits of ZnO nanowires and CuO nanofilms are due to composition and geometry distribution difference between dezincified Cu70Zn30 grain surface and grain boundary, resulting in heterogeneous surface oxidation kinetics of Cu and Zn element. The surface dezincification and selective oxidation process could provide a new approach for heterogeneous nanostructure design, fabrication, and control. These semiconductor nanowire/film network junctions may be used as nanoscale building block for electronic and optoelectronic devices.