Semiconductor device having bipolar transistors

A semiconductor device comprising:

• a semiconductor substrate that is comprised an SOI substrate having a support layer, an element forming layer and a burying oxide layer that is disposed between the support layer and the element forming layer;
• an NPN bipolar transistor formed on the element forming layer of the substrate in an NPN forming region and having a n type emitter region, a n type collector region and an p type base region;
• a PNP bipolar transistor formed on the element forming layer of the substrate in a PNP forming region and having an p type emitter region, an p type collector region and a n type base region;
• at least one trench formed in the element forming layer for isolating between the NPN bipolar transistor and the PNP bipolar transistor;
• and
• only one conductive type burying region formed in at least one of the NPN forming region and the PNP forming region;
• wherein a current that flows from the p type emitter region to the n type base region in the PNP transistor flows in the n type base region in a direction perpendicular to the substrate.

A semiconductor device comprising:

• a semiconductor substrate;
• an NPN bipolar transistor formed on the substrate in an NPN forming region and having an n type emitter region, an n type collector region and a p type base region;
• a PNP bipolar transistor formed on the substrate in a PNP forming region and having a p type emitter region, a p type collector region and an n type base region;
• and
• wherein a current that flows from the p type emitter region to the n type base region in the PNP transistor flows in the n type base region in a direction perpendicular to the substrate, and
• wherein the NPN forming region and the PNP forming region have no conductive type burying region.