The recent development of research in 2-dimensional (2D) semiconducting materials based on semiconducting transition metal dichalcogenides (TMDCs) enables a novel engineered quantum structures. Employing functional interface realized in high-quality van der Waals (vdW) heterostructures, gate-defined electronic systems can be fabricated. In particular, spatially confined quantum structures in TMDC can offer unique valley-spin features, holding the promises for novel mesoscopic systems, such as valley-spin qubits. In this presentation, we report the fabrication of the gate-defined quantum structures formed in atomically thin TMDC heterostructures, exhibiting quantum transport phenomena and optoelectronic processes. For this work, we have developed several experimental innovations, including stamping the TMDC channel to the local gate electrodes, encapsulation of channel in 2D dielectrics, and light illumination at low temperatures, which lead to a vast improvement in the quality of the TMDC heterostructures. We report several unusual quantum transport phenomena in the TMDC heterostructures, such as the quantized conductance in gate-tunable quantum confinement in a quantum point contacts and single electron charging with tunable tunnel-coupling. We also report tunable optoelectronic processes in confined quantum structures in 2D TMDCs.