intrinsic collector 110 and sinker protection film 106 an intrinsic sige film a p type extrinsic sige and an intrinsic silicon film may be sequentially grown so that the sige base layer 111 is formed base layer 111 may have a thickness of about 50 nm to about 100 nm in total the concentration of ge may be in the range of 1 to about 20 the doping concentration of p type dopant such as boron b may be in the range of 10 19 cm u2212 3 to about 3 u00d7 10 20 cm u2212 3 fig3 d subsequently buffer protection film 112 may be evaporated on the entire surface of sige base layer 111 by a low pressure chemical vapor deposition lpcvd method fig3 e buffer protection film 112 may be dry etched until the upper surface of base electrode 108 is reached so that masking film 112 a is formed fig3 f the portion of base layer 111 that is not masked by masking film 112 a may be removed by dry etching then masking film 112 a may be removed by wet etching thereby exposing the remaining portion of base layer 111 thereafter by employing a low pressure chemical vapor deposition method lpcvd first sidewall film 113 which may comprise a silicon oxide film or a silicon nitride film with a thickness of about 50 nm about 300 nm may be formed to separate base and emitter second sidewall film 114 may be formed by thickly evaporating a silicon oxide film or a silicon nitride film the thickness of second sidewall film 114 may be about 200.