Semiconductor device and method for fabricating the same

A semiconductor device comprising:

• an SOI substrate that is a substrate including a base substrate, an insulating layer, and a semiconductor layer laminated in this order, in which circuit elements are formed over a main surface of the semiconductor layer;
• a first semiconductor island that is isolated from other semiconductor layers by element isolation grooves in a first region of the semiconductor layer of the SOI substrate, a first group of semiconductor islands including a plurality of semiconductor islands that are made identical in size to the first semiconductor island by element isolation grooves in a second region of the semiconductor layer, and a second group of semiconductor islands including a plurality of semiconductor islands that are made identical in size to the first semiconductor island by element isolation grooves in a third region of the semiconductor layer;
• a plurality of unit bipolar transistors being identical in size and formed on the first semiconductor island, and each of the plurality of the semiconductor islands included in the first and second group, the unit bipolar transistors having the emitter, base, and collector regions formed in the first, second, and third regions of the semiconductor layer;
• first interconnection wiring for causing the unit bipolar transistors in the first region of the semiconductor layer to function as a first transistor having first electrical characteristics by itself, and a second interconnection wiring for connecting the emitter, base, and collector regions of the unit bipolar transistors of the first group in the second region of the semiconductor layer in parallel to cause them to function in combination as a second transistor having second electrical characteristics;
• and
• third interconnection wiring for connecting the emitter, base, and collector regions of the unit bipolar transistors of the second group in the third region of the semiconductor layer in parallel to cause them to function in combination as a third transistor having third electrical characteristics.

A semiconductor device comprising:

• an SOI substrate including an insulating layer laminated on a semiconductor layer, in which circuit elements are formed over a main surface of the semiconductor layer;
• a plurality of semiconductor islands used as element-forming regions, the semiconductor islands being of identical size, and being mutually isolated by element isolation grooves that cross the semiconductor layer and reach the insulating layer of the SOI substrate;
• a plurality of unit bipolar transistors formed in respective semiconductor islands, having a size matching the size of the semiconductor islands, and having respective emitter, base, and collector regions formed on the main surface of the semiconductor layer;
• and
• interconnection wiring for connecting the emitter, base, and collector regions of the plurality of unit bipolar transistors in parallel and causing them to function in combination as one transistor having desired electrical characteristics;
• wherein
• the plurality of semiconductor islands being disposed in pairs on the main surface of the semiconductor layer and the base region of each unit bipolar transistor in each of the paired semiconductor islands being electrically connected with a base lead electrode integrally patterned on the space between the pair of semiconductor islands, which are disposed adjacent to each other.

A semiconductor device comprising:

• an SOI substrate having an insulating layer laminated on a semiconductor layer, in which circuit elements are formed over a main surface of the semiconductor layer;
• a plurality of semiconductor islands used as element-forming regions, the semiconductor islands being of identical size, and being mutually isolated by element isolation grooves crossing the semiconductor layer and reaching the insulating layer of the SOI substrate;
• a plurality of unit bipolar transistors formed in respective semiconductor islands, having a size matching the size of the semiconductor islands, and having respective emitter, base, and collector regions formed on the main surface of the semiconductor layer;
• and
• interconnection wiring for connecting the emitter, base, and collector regions of the plurality of unit bipolar transistors in parallel and causing them to function in combination as one transistor having desired electrical characteristics,
• wherein each of the plurality of the semiconductor islands includes a pair of unit bipolar transistors.

A method of fabricating a semiconductor device comprising the steps of:

• (a) providing a plurality of electrically isolated semiconductor islands of identical size in a semiconductor layer formed on an insulating layer;
• (b) fabricating a device by electrically interconnecting unit bipolar transistors, the unit bipolar transistors of identical type being formed in respective semiconductor islands and having emitter, base, and collector regions formed on the main surface of the semiconductor layer, to form a plurality of transistors with desired electrical characteristics;
• (c) carrying out circuit simulation of the device;
• and
• (d) determining the number of unit bipolar transistors to be connected in parallel to form the plurality of transistors having the desired electrical characteristics.