Abstract: A plurality of photo diodes PD1 to PD4 are formed on a p-type silicon substrate. The photo diodes PD1 to PD4 are electrically isolated from one another by lower and upper isolation regions 3 and 5. Arms of strip portions of each of the lower and upper isolation regions 3 and 5 are narrowed in width toward the center of an intersection of the strip portions in a plane. Thereby, there can be provided a semiconductor device which can efficiently convert laser light for illumination to photovoltage.

Abstract: A photoresist pattern is formed on a field oxide film and an element forming region across the field oxide film and the element forming region such that a portion of a surface of the field oxide film and a portion of a surface of a silicon epitaxial layer are continuously exposed. The photoresist pattern is used as a mask to inject boron ions into the silicon epitaxial layer and heat treatment is performed thereon to form an external base containing the relatively significant crystal defect present in the silicon epitaxial layer in the vicinity of the field oxide film. Thus, a semiconductor device can be obtained including a bipolar transistor which provides improved breakdown voltage between the collector and the base and contemplates reduction of current leakage.

Abstract: A photoresist pattern is formed on a field oxide film and an element forming region across the field oxide film and the element forming region such that a portion of a surface of the field oxide film and a portion of a surface of a silicon epitaxial layer are continuously exposed. The photoresist pattern is used as a mask to inject boron ions into the silicon epitaxial layer and heat treatment is performed thereon to form an external base containing the relatively significant crystal defect present in the silicon epitaxial layer in the vicinity of the field oxide film. Thus, a semiconductor device can be obtained including a bipolar transistor which provides improved breakdown voltage between the collector and the base and contemplates reduction of current leakage.