Creating a new spin-based electronics (often called "spin-electronics" or "spintronics") is one of the hot topics in the current solid-state physics and electronics research. In order to utilize the spin degree of freedom in solids, particularly in semiconductors the current electronics is based on, we need to fabricate appropriate materials, understand the spin-dependent phenomena, and control the spins. In this talk, I will review the recent developments of epitaxial ferromagnetic heterostructures based on semiconductors towards spintronics. This includes the semiconductor materials and heterostructures having high ferromagnetic transition temperature (III-V based alloy magnetic semiconductors, Mn-delta-doped magnetic semiconductors, and related heterostructures), spin-dependent transport and tunneling, spin-dependent bandgap engineering, their device applications (tunneling magnetoresistance devices and three-terminal devices). Future issues and prospects will be also discussed. @FootnoteText@ The author thanks the collaborations and discussions with S. Sugahara, A.M. Nazmul and Y. Higo, S. Ohya, and T. Matsuno. The work at the Univ. of Tokyo was partially supported by PRESTO of JST, IT Program of MEXT, Toray Science Foundation.