A Near-Field Scanning Microwave Microscope (NSMM) for the characterization of semiconductor structures has been designed, simulated and fabricated. The present NSMM system is based on a home-made coaxial-cavity resonator which is fed by a Keysight N5242A PNA-X Network Analyzer. The inner conductor of the coaxial resonator is connected to a sharpened tungsten tip, which was fabricated by an electrochemical process. The reflection and transmission coefficients S-11, S-21, the resonance frequency f(r) and the quality factor Q of the resonant cavity are measured as the semiconductor structure is scanned by the sharpened probe tip while the sample-tip distance is kept constant in the near-field region. The interaction between the probe tip and the sample under test provides variations of these parameters which are related to the topographical and dielectric properties of a very small region of the material under the probe tip. Thus, a 2D image of the evolution of the S-11, S-21, f(r) and Q parameters on the surface of the device under test is obtained. This image can be related to space changes in the topography, dielectric properties and composition of the semiconductor structure.