| 摘要 |
PURPOSE:To integrate two transistors of different frequency band with each other, by providing base regions of different diffusion depth in a semiconductor substrate. CONSTITUTION:N-type buried regions 4, 4' are produced by diffusion in a P-type silicon substrate 1. An N-type layer is epitaxially grown. The layer is divided into insular regions 13c, 13c' by P-type separating regions 2-2''. An SiO2 film 6 is coated on the substrate 1. The thickness of the film 6 is large on the peripheral parts of the insular regions 13c, 13c' but small on their central parts. A resist film 10 having a hole 10b is coated on a base resion making part for a first transistor. A P-type ion implantation region 13b is made in the insular region 13c and elongated by heat treatment, thereby producing a P-type base region 23b of large depth. A P-type base region 23b' of small depth for a second transistor is produced in the insular region 13c' in the same manner as the former base region 23b. An Si3N4 film 8 is then coated on the entire surface. Holes are opened through the film 8 so that N-type emitter regions 3e, 3e' for the first and the second transistors are produced in the regions 23b, 23b' by diffusion. |
