Dynamic random access memory with buried bit line and method for forming the same

Abstract

A method for forming a Dynamic Random Access Memory (DRAM) includes forming an isolation structure in a substrate to define an active region. The method also includes forming a bit line trench in the active region to divide two active pillars. The method also includes forming a buried bit line in the bit line trench. The method also includes forming an insulating material over the bit line in the bit line trench. The top surface of the insulating material is lower than the top surface of the substrate. A trench is formed over the insulating material. The method also includes forming a shallow recess on the sidewalls of each of the active pillars exposed by the trench to make that each of the active pillars has a neck channel region. The method also includes forming a buried word line in the shallow recess.