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Nanostructures with high electrical conductivity were fabricated on silicon surfaces using a laser-assisted scanning tunneling microscope (LA-STM). The nanostructures, dots and lines, were fabricated on H-passivated p-doped silicon (110) surfaces. By precisely controlling the experimental conditions such as pulse energy and tip-surface gap distance, feature sizes (dot diameters and line widths) and heights of the fabricated nanostructures could be controlled. For instance, a dot with a diameter of 30 nm and a line with a width of 30 nm were obtained. In addition, scanning tunneling microscopy investigation of the structures revealed that their band gaps were changed during the LA-STM process. As a consequence, the local conductivity (more precisely the tunneling probability) was enhanced. Numerical simulations based upon the finite-difference-time-domain algorithm provide detailed insight into the spatial distribution of the enhanced optical field underneath the STM tip and associated physical phenomena. Potential applications of the developed nanostructuring process are anticipated in various nanotechnology fields, particularly in the field of nanoelectronics.