Patent ID: 8236648
Filing Date: 2012-08-07
Classification: H01L

Abstract:
1. A method of manufacturing a semiconductor device comprising: preparing a semiconductor substrate having a first conductivity type; removing a portion of the semiconductor substrate to form a channel region and forming a trench portion having a side surface and a bottom surface wherein a planar portion is disposed in the semiconductor substrate other than the trench portion; forming an oxide film on a surface of the trench portion and a surface of the planar portion; applying a resist material and patterning the resist material such that an impurity can be introduced through the trench portion in a source region direction and a drain region direction; prior to forming a gate electrode, ion-implanting an impurity having a second conductivity type in the source region direction and in the drain region direction using the resist material as a mask to form a source region and a drain region; removing the resist material and the oxide film and forming a gate insulating film; depositing polycrystalline silicon to form the gate electrode on the gate insulating film; patterning the gate electrode to entirely occupy a cavity defined by the side surface and the bottom surface of the trench portion and the planar portion, the gate electrode having a varying gate length dimension, such that the gate length of a first transistor portion in the cavity is longer than the gate length of a second transistor portion on the planar portion; and performing heat treatment for diffusion and activation of the source region and the drain region from the side surface of the trench portion down to the bottom surface.