| 摘要 |
A polysilicon self-aligned transistor has a polysilicon layer (24) with a cavity (30) formed therein. To form the polysilicon layer (24) with a cavity (30), a thin seed layer (14) is disposed over an epitaxial layer (11a). Dielectric layers (16, 18) are formed over the seed layer (14), and are subsequently etched to define the polysilicon layer (24) and the cavity (30). The cavity (30) is defined by a dielectric plug (22). The exposed seed layer (14) is used to selectively grow the polysilicon layer (24). Thereafter, the dielectric plug (22) is removed to form the cavity (30) through which the base (32) is implanted into the substrate (12) and the emitter (36) is formed.
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