| 摘要 |
<p>A bipolar transistor (60) with a relatively deep emitter region (62) is formed in a BICMOS device (64) using the source/drain mask used to form the source and drain regions (44, 46) of MOSFETs of the device and the base region mask which would otherwise be required in any event to diffuse an emitter region (62) of the bipolar transistor (60). The emitter (62) is diffused or implanted to a depth greater than the depth to which a source and a drain region (44, 46) of the MOSFET (26) are diffused. By using only the base region (32) and source/drain region masks, and developing in sequence, each of two coatings of photoresist applied on top of one another, an access opening to the emitter region (62) is defined solely by the co-location of openings in each of the two coatings, thereby allowing the emitter region (62) to be separately and additionally implanted. The access to the base region (32) for the additional implantation is achieved using only a few additional photo-ops and not as a result of using an additional emitter mask.</p> |
