Semiconductor device and method of manufacturing the same
A semiconductor device comprises a pillar layer including first semiconductor pillars of a first conduction type and second semiconductor pillars of a second conduction type formed laterally, periodically and alternately. The first and second semiconductor pillars include a plurality of diffusion layers formed in a third semiconductor layer as coupled along the depth. The diffusion layers have lateral widths varied at certain periods along the depth. An average of the lateral widths of the diffusion layers in one certain period is made almost equal to another between different periods.
1. A semiconductor device, comprising:
a first semiconductor layer of a first conduction type;
a pillar layer including first semiconductor pillars of the first conduction type and second semiconductor pillars of a second conduction type formed laterally, periodically and alternately on the first semiconductor layer;
a first main electrode electrically connected to the first semiconductor layer;
a semiconductor base layer of the second conduction type formed selectively on a surface of said pillar layer;
a second semiconductor layer of the first conduction type formed selectively on a surface of said semiconductor base layer;
a second main electrode electrically connected to said second semiconductor layer and said semiconductor base layer; and
a control electrode formed along said semiconductor base layer with an insulator interposed therebetween to form a channel between said second semiconductor layer and said first semiconductor pillar,
wherein said first or second semiconductor pillars include a plurality of diffusion layers periodically formed in a third semiconductor layer for a plurality of periods along a depth direction, said plurality of diffusion layers being coupled along the depth direction, a number of said diffusion layers being formed in one of said periods, said third semiconductor layer formed on said first semiconductor layer,
wherein each of said plurality of diffusion layers in one of the periods has a lateral width in a direction substantially perpendicular to said depth direction different from one another, and
wherein an average of said lateral widths of said diffusion layers in one of said periods is made almost equal to that in another one of said periods.
2. The semiconductor device according to claim 1 , wherein at least one period is different in balance of impurity concentrations between said first and second semiconductor pillars.
3. The semiconductor device according to claim 1 , wherein said plurality of diffusion layers have vertical depths varied at certain periods along the depth, wherein an average of said vertical depths of said diffusion layer in one of said certain periods is made almost equal to another between different periods.
4. The semiconductor device according to claim 1 , wherein said diffusion layer has a high impurity concentration in part.
5. The semiconductor device according to claim 1 , wherein at least one period is different in balance of impurity concentrations between said first and second semiconductor pillars.
6. The semiconductor device according to claim 1 , wherein said control electrode is formed on said surface of said semiconductor base layer with said insulator interposed therebetween.
7. The semiconductor device according to claim 1 , wherein said gate electrode is formed by burying a conductive layer in a trench with said insulator interposed therebetween, said trench reaching said first semiconductor pillars through said semiconductor base layer.
8. The semiconductor device according to claim 1 , wherein said first and second semiconductor pillars are formed in the shape of stripes extending in the same direction.
9. The semiconductor device according to claim 1 , wherein said first and second semiconductor pillars are formed in the shape of a grid or zigzag in section along said first semiconductor layer.
10. The semiconductor device according to claim 1 , wherein said first and second semiconductor pillars are also formed in an end region surrounding a device forming region.
11. The semiconductor device according to claim 10 , wherein said first and second semiconductor pillars in said end region are formed at narrower periods than in said device forming region.
12. The semiconductor device according to claim 10 , wherein said first and second semiconductor pillars in said end region have depths decreasing with distance from said device forming region.
13. The semiconductor device according to claim 10 , wherein said first or second semiconductor pillars in said end region have lateral widths made larger on the side close to said second main electrode than on the side close to said first main electrode.
14. The semiconductor device according to claim 10 , wherein said first or second semiconductor pillars have distribution of impurity concentrations, the distribution having several peaks in one of the periods, and the distances between the peaks are different from one another in one of the periods.
15. A semiconductor device, comprising:
a first semiconductor layer of a first conduction type;
a pillar layer including first semiconductor pillars of the first conduction type and second semiconductor pillars of a second conduction type formed laterally, periodically and alternately on said first semiconductor layer;
a first main electrode electrically connected to said first semiconductor layer;
a semiconductor base layer of the second conduction type formed selectively on a surface of said pillar layer;
a second semiconductor layer of the first conduction type formed selectively on a surface of said semiconductor base layer;
a second main electrode electrically connected to said second semiconductor layer and said semiconductor base layer; and
a control electrode formed along said semiconductor base layer with an insulator interposed therebetween to form a channel between said second semiconductor layer and said first semiconductor pillars,
wherein said first or second semiconductor pillars include a plurality of diffusion layers formed in a third semiconductor layer as coupled along a depth direction, said third semiconductor layer formed on said first semiconductor layer,
wherein said third semiconductor layer includes a plurality of stacked epitaxial layers,
wherein said plurality of diffusion layers are arrayed along the depth direction in each one of said epitaxial layers, each of said diffusion layers in one of said epitaxial layers has a lateral width in a direction substantially perpendicular to said depth direction different from one another,
wherein the plurality of diffusion layers have distributions of impurity concentration, the distributions having several peaks in one of said epitaxial layers, and
wherein R>T/2 is realized where T denotes a thickness of any one of said epitaxial layers, and R denotes a distance between said peaks in the uppermost layer and the lowermost layer in said one epitaxial layer with the thickness T.
16. The semiconductor device according to claim 15 , wherein T−R>Wave×0.3 is realized where Wave denotes an average of widths of a plurality of diffusion layers arrayed along the depth in one epitaxial layer.