Abstract: A transistor for a phase change memory device includes a semiconductor substrate in which active regions are delimited by an isolation structure. A groove is defined on a surface of a gate forming area of each active region. Portions of the isolation structure, which are adjacent to the gate forming area of the active region, are recessed to expose side faces of the gate forming area of the active region. A gate is formed on the gate forming area of the active region over the gate forming area grooves and exposed side faces thereof as well as the recessed portions of the isolation structure. Junction areas are then formed in the active region on both sides of the gate to complete the transistor of a phase change memory device.