Semiconductor device and method of manufacturing the same
View Patent ↗In a semiconductor device according to the present invention, two epitaxial layers are formed on a P type substrate. In the substrate and the epitaxial layers, isolation regions are formed to divide the substrate and the epitaxial layers into a plurality of islands. Each of the isolation regions is formed by connecting first and second P type buried layers with a P type diffusion layer. By disposing the second P type buried layer between the first P type buried layer and the P type diffusion layer, a lateral diffusion width of the first P type buried layer is reduced. By use of this structure, a formation region of the isolation region is reduced in size.
1. A semiconductor device comprising:
a one-conductivity-type semiconductor substrate;
a first opposite-conductivity-type epitaxial layer formed on the semiconductor substrate;
a second opposite-conductivity-type epitaxial layer formed on the first epitaxial layer; and
a one-conductivity-type isolation region dividing the first and second epitaxial layers into a plurality of islands,
wherein the isolation region is formed by connecting a first one-conductivity-type buried diffusion layer formed across the semiconductor substrate and the first and second epitaxial layers, a second one-conductivity-type buried diffusion layer formed in the second epitaxial layer, and a first one-conductivity-type diffusion layer formed in the second epitaxial layer.
2. The semiconductor device according to claim 1 , wherein
a bipolar transistor is formed in one of the islands, and
an opposite-conductivity-type buried diffusion layer formed across the first and second epitaxial layers, and an opposite-conductivity-type diffusion layer formed in the second epitaxial layer are formed to connect with each other between the isolation region and a second one-conductivity-type diffusion layer used as a base region of the bipolar transistor.
3. The semiconductor device according to claim 2 , wherein
the opposite-conductivity-type buried diffusion layer and the opposite-conductivity-type diffusion layer are disposed so as to surround the second one-conductivity-type diffusion layer, and
a collector electrode of the bipolar transistor is connected to the opposite-conductivity-type diffusion layer.
4. The semiconductor device according to claim 1 , wherein
the first one-conductivity-type buried diffusion layer and the first one-conductivity-type diffusion layer partially overlap with each other in the second epitaxial layer,
an impurity concentration peak of the first one-conductivity-type buried diffusion layer is positioned closer to the substrate than a center of the total thickness of the first and second epitaxial layers, and
an impurity concentration peak of the second one-conductivity-type buried diffusion layer and an impurity concentration peak of the first one-conductivity-type diffusion layer are positioned closer to a surface of the second epitaxial layer than the center.
5. The semiconductor device according to claim 4 , wherein
the second one-conductivity-type buried diffusion layer has the impurity concentration peak positioned closer to the surface of the second epitaxial layer than the overlapping region of the first one-conductivity-type buried diffusion layer and the first one-conductivity-type diffusion layer, and
the second one-conductivity-type buried diffusion layer is formed to overlap with the first one-conductivity-type buried diffusion layer and the first one-conductivity-type diffusion layer, thus including the overlapping region.
6. The semiconductor device according to any one of claims 4 and 5 , wherein
a bipolar transistor is formed in one of the islands,
an opposite-conductivity-type diffusion layer is formed between the isolation region and a second one-conductivity-type diffusion layer used as a base region of the bipolar transistor, and
the second one-conductivity-type buried diffusion layer forms a junction region with the opposite-conductivity-type diffusion layer.
7. The semiconductor device according to claim 6 , wherein
the opposite-conductivity-type diffusion layer is disposed so as to surround the second one-conductivity-type diffusion layer, and
the junction region is formed across a formation region of the opposite-conductivity-type diffusion layer.
8. A semiconductor device comprising:
a one-conductivity-type semiconductor substrate;
a first opposite-conductivity-type epitaxial layer formed on the semiconductor substrate;
a second opposite-conductivity-type epitaxial layer formed on the first epitaxial layer; and
a one-conductivity-type isolation region dividing the first and second epitaxial layers into a plurality of islands,
wherein the isolation region is formed by connecting a first one-conductivity-type buried diffusion layer formed across the semiconductor substrate and the first and second epitaxial layers, a second one-conductivity-type buried diffusion layer formed in the second epitaxial layer, and a first one-conductivity-type diffusion layer formed in the second epitaxial layer, and
a bipolar transistor is formed in one of the islands, and
an opposite-conductivity-type diffusion layer is formed between the isolation region and a second one-conductivity-type diffusion layer used as a base region of the bipolar transistor.
9. The semiconductor device according to claim 8 , wherein
the opposite-conductivity-type diffusion layer is disposed so as to surround the second one-conductivity-type diffusion layer, and
a collector electrode of the bipolar transistor is connected to the opposite-conductivity-type diffusion layer.