An experimental study of p-La0.7Ca0.3MnO3/ SrTiO3/n-Si heterostructure in which the LCMO and Si are separated by a thin interfacial SrTiO3 (STO) layer with typical thickness of about 15 nm, has been in situ fabricated with the Pulsed laser deposition technique. The La0.7Ca0.3MnO3 (LCMO) film of about 70 nm has been grown on STO at substrate (n-Si) temperature of 800°C in 0.5 mbar oxygen pressure. The junction exhibits good rectifying behavior over the temperature range of 10 – 300 K. Electrical properties of p-La0.7Ca0.3MnO3/STO/n-Si MOS like heterostructure exhibits nonlinear I-V characteristics in a wide temperature range. The heterostructure also exhibits MOS-diode like behavior with all type of possible current flow mechanisms (such as thermionic emission, tunneling, recombination, degeneration, etc.) through the heterojunction. The ideality factor, reverse saturation current, series resistances and turn-on voltages of the heterojunction have been estimated at different operating temperatures. The junction magnetoresistance (JMR) properties of p-LCMO/STO/n-Si heterostructure have been studied over the temperature range of 100-300 K. The current-voltage characteristics at all temperatures conclusively show the high sensitivity junction magnetoresistance (JMR – 48% at 150 K and ~ 30% at 300 K) under the external 7 T magnetic field. The JMR is positive and strongly depends on temperature at an applied forward bias voltage (3 V). The relation between JMR and external magnetic field is found to be of (Δρ/ρ ≈ α Hβ) type having both α and β temperature dependent. We attribute the emergence of positive JMR to the quantum mechanical tunneling transport mechanism along with the modification of barrier height across the heterojunction.