Semiconductor device including a transistor with gate in a trench and a doped region under the trench to modify the threshold voltage

摘要

A semiconductor device includes a transistor with a substrate on which source and drain regions, both of a first conductivity type, and a channel region of a second conductivity type between the source and drain are formed, and a gate electrode formed in the channel region to bury a trench formed so the depth thereof changes intermittently in the width direction of the gate. In the channel region, each on a surface of the substrate and in a bottom portion of the trench, there are formed a second high-concentration region and a first high-concentration region, and the dopant concentration of the second conductivity type is higher than the dopant concentration of the second conductivity type in portions sideward from the trench. The dopant concentration of the second conductivity type in the first high-concentration region is higher than the dopant concentration of the second conductivity type in the second high-concentration region.

主权项

1. A semiconductor device comprising:
a source region and a drain region, both of which are of a first conductivity type and formed in a substrate; a channel region of a second conductivity type formed in the substrate and arranged, in a plane view, in a first direction between the source region and the drain region; a trench formed in the substrate between the source region and the drain region and having a side surface of the trench extending in the first direction between the source region and the drain region; a gate insulating film formed in the trench; a gate electrode formed in the trench through the gate insulating film such that a portion of the channel region sideward, in a second direction crossing and being in a same plane as the first direction, from the side surface of the trench, in the first direction both the source region and the drain region and is arranged between the source region and the drain region; and a buried region of the second conductivity type formed directly below the trench, directly below the source region and directly below the drain region such that the buried region contacts a bottom portion of the trench and device isolation regions, and that a dopant concentration of the second conductivity type of the buried region is higher than a dopant concentration of the second conductivity type of the portion of the channel region sideward from the side surface of the trench.