The present invention provides a micro-heater array and pn-junction devices having micro-heater arrays, and methods for fabricating the same. The invention includes: micro-heater arrays including first and second micro-heaters disposed perpendicular to or parallel with each other on a substrate and methods of fabricating PN junctions between first and second heating portions using the heat generated from the first and second heating portions, respectively, when applying a voltage to the micro-heater array. Accordingly, when forming PN junctions using micro-heaters, a high-quality PN junction may be fabricated on a glass substrate over a large area.