Memories having a charge storage node at least partially located in a trench in a semiconductor substrate and electrically coupled to a source/drain region formed in the substrate

Abstract

A memory charge storage node () is at least partially located in a trench (). The memory comprises a transistor including a source/drain region () present at a first side () but not a second side () of the trench. Before forming conductive material () providing at least a portion of the charge storage node, a blocking feature () is formed adjacent to the second side () to block the conductive material (). The blocking feature can be dielectric left in the final structure, or can be a sacrificial feature which is removed after the conductive material deposition to make room for dielectric. The blocking features for multiple trenches in a memory array can be patterned using a mask () comprising a plurality of straight strips each of which runs through the memory array in the row direction. The charge storage node has a protrusion () at the first side of the trench adjacent to the source/drain region and also has a top surface portion (T) laterally adjacent to the protrusion. The trench sidewall has a substantially straight portion (S) on the second side () rising above the top surface portion (T). The dielectric () on the trench sidewall has a portion () which is thicker on the second side than on the first side of the trench.