We have fabricated hybrid structures consisting of a metallic thin film and of a microstructured two-dimensional electron system in an InAsheterostructure. The devices are found to exhibit a huge magnetoresistance(MR)effect in magnetic fields ⩽1 T . At low temperature, a value of ΔR/R=[R(B=1 T )−R(B=0)]/R(B=0) as high as 115 000% is measured. The value of ΔR/R has been studied as a function of the electron mobility, the electron density and the lateral width of the semiconductor. We find that the MReffect can be tailored by these different parameters and technological relevant devices can be realized.