Buried strap with limited outdiffusion and vertical transistor DRAM

摘要

A DRAM cell with a vertical transistor forms a buried strap outdiffusion with reduced lateral extent by shifting high temperature steps that affect the thermal budget before the initial buried strap diffusion. The gate conductor is formed in two steps, with poly sidewalls being put down above a sacrificial Trench top oxide to form a self-aligned poly-gate insulator structure before the formation of the LDD extension.