Miniaturized thin-film germanium strain gauges have been fabricated. Solid-source diffusion is used to incorporate a controlled amount of aluminum as p-type doping. This facilitates simple and precise control of film conductivity and results in better matching from batch to batch. Thermal sensitivity of the sensors is also minimized in this manner. Values of the temperature coefficient of resistance (TCR) less than 200 ppm/°C are achieved, while the longitudinal gauge factor is higher than 10. A new micro-soldering technique is also introduced, which provides the strong and flexible connections desired for mechanical sensors. In addition, the effect of copper-induced crystallization on the piezoresistivity of germanium films has been studied. Longitudinal gauge factors as high as 54 are obtained upon annealing a bilayer of Cu and Ge and subsequently etching away the copper germanide layer and any unreacted Cu.