This invention pertains to electronic/optoelectronic devices with reduced extended defects and to a method for making it. The device includes a substrate, a semiconductor active material deposited on said substrate, and electrical contacts. The semiconductor active material defines raised structures having atomically smooth surfaces. The method includes the steps of depositing a dielectric thin film mask material on a semiconductor substrate surface; patterning the mask material to form openings therein extending to the substrate surface; growing active material in the openings; removing the mask material to form the device with reduced extended defect density; and depositing electrical contacts on the device.