We have fabricated hybrid structures consisting of a metallic thin film and of a microstructured two-dimensional electron system in an InAs heterostructure. The devices are found to exhibit a huge magnetoresistance (MR) effect in magnetic fields ≤1T. At low temperature, a value of ΔR/R=[R(B=1T)-R(B=0)]/R(B=0) as high as 115000% 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 MR effect can be tailored by these different parameters and technological relevant devices can be realized.