Semiconductor device and method for fabricating the same
A semiconductor device includes: a semiconductor substrate; a first semiconductor region formed in the reverse surface region of the semiconductor substrate and including a first conductivity type impurity; a second semiconductor region formed on the first semiconductor region in the semiconductor substrate and including a second conductivity type impurity; a third semiconductor region formed on the second semiconductor region in the semiconductor substrate and including a first conductivity type impurity; a trench passing through the second and third semiconductor regions and reaching the first semiconductor region; and a gate insulating film formed along the wall face of the trench; a gate electrode formed on the gate insulating film in the trench. Further, a pocket region including a second conductivity type impurity of which peak concentration is higher than that of the second semiconductor region is formed by a side of the trench between the second semiconductor region and the third semiconductor region.
1. A semiconductor device, comprising:
a semiconductor substrate;
a first conductivity type drain region provided in a lower part of said semiconductor substrate;
a second conductivity type substrate region provided on said drain region in said semiconductor substrate;
a first conductivity type source region provided on said substrate region in said semiconductor substrate;
a trench formed in said semiconductor substrate and reaching said drain region;
a gate insulating film provided at least on a side wall of said trench;
a gate electrode provided on said gate insulating film in said trench;
a second conductivity type pocket region provided between said substrate region and said source region and being in contact with said source region;
an insulating film formed in said trench to cover said gate electrode and having an upper end located lower than an upper surface of said semiconductor substrate;
a source electrode provided above said source region; and
a second conductivity type high concentration substrate region formed so as to be adjacent to said source region on said substrate region in said semiconductor substrate and having an impurity concentration higher than that of said substrate region,
wherein said gate insulating film is in contact with said substrate region and said pocket region at said side wall of said trench, and
said source electrode is in contact with an upper surface of said source region, and in contact with a portion of a side surface of said source region which is located above said upper end of said insulating film in said trench.
2. The semiconductor device of claim 1 , wherein said pocket region is formed only under a portion of said source region, the portion being close to said side wall of said trench.
3. The semiconductor device of claim 1 , wherein
said pocket region is formed under an entire portion of said source region.
4. The semiconductor device of claim 1 , wherein said pocket region has a peak of impurity concentration higher than that of said substrate region.
5. The semiconductor device of claim 1 , wherein said drain region includes: a first conductivity type high concentration drain region; and a first conductivity type low concentration drain region provided on said high concentration drain region.
6. The semiconductor device of claim 1 , wherein
said source electrode is made of a suicide film.
7. The semiconductor device of claim 1 , wherein
an upper end of a part where said gate electrode is in contact wit said gate insulating film is located upper than a boundary between said source region and said pocket region.
8. The semiconductor device of claim 1 , wherein a peak of impurity concentration of said pocket region is located close to said gate insulating film in a direction perpendicular to the depth direction of said trench in said semiconductor substrate.
9. The semiconductor device of claim 1 , wherein said substrate region is to be a channel region.