Trenched bipolar transistor structures

摘要

Both homojunction and heterojunction bipolar transistor structures are fabricated in unique trenched configurations so as to better utilize their surface areas by employing both the vertical and horizontal portions of their base regions with equal effectiveness. An important advantage of the unique trenched configurations is that the base region of each trenched structure is of precisely the same thickness throughout-both vertical and horizontal portions. Consequently, the transit time for charge carriers to diffuse across the base region and the base transport factor are uniform because of the uniform base thickness. Moreover, the parasitic capacitance region of each trenched structure beneath base metallization contacts is only a small portion of the entire base-collector junction region. Accordingly, the RC time constant of each trenched structure is very low and the high frequency response gain of the heterojunction trenched bipolar transistor structure is an order of magnitude higher than its conventional heterojunction bipolar transistor counterpart.