A thin film magnetic read/write head is manufactured using Al.sub.2 O.sub.3 dams. The Al.sub.2 O.sub.3 dams are formed using a sacrificial layer which is deposited upon a bottom pole layer. An Al.sub.2 O.sub.3 layer is deposited over the sacrificial layer. When the sacrificial layer is removed, the Al.sub.2 O.sub.3 layer forms dams between which a top pole piece is deposited. The sacrificial layer is removed using lapping and a selected chemical etch; partial lapping or chemical etch followed by chemical etch of the sacrificial layer which lifts-off overlying Al.sub.2 O.sub.3 ; depositing photoresist dams and chemically etching the encapsulation layer and the sacrificial layer; or removal through physical or thermal shock of the Al.sub.2 O.sub.3 layer sputtered at zero bias followed by a selective chemical etch of the sacrificial layer.