This chapter covers my current understanding of the research and development of phase-change random access memory (PCRAM): principle, history, phase-change material, device structure, processing, characteristic, future outlook, and application. In the foreword, the major past and present status perspectives of phase-change materials are discussed. Section 11.2 presents the principles of PCRAM. Comparisons between PCRAM and synchronous RAM (SRAM), the dynamic RAM (DRAM), and FLASH are discussed in Section 11.3. Section 11.4 provides a discussion of the history of PCRAM R&D. The detailed development of phase-change materials is provided in Section 11.5. The structure of memory cell selector and resistor are provided in Sections 11.6 and 11.7. In Section 11.8, the processing of memory cell resistor is provided. The understandings of characteristics of PCRAM memory cell are the subject of Section 11.9. Section 11.10 provides a discussion of
PCRAM future outlook device. Finally, potential applications of PCRAM are briefly introduced in Section 11.11.