u00b0 c so that thermal flow provides a resist pattern having a forwardly tapered cross sectional profile any material such as metal oxide or resin other than resists can be used as the mask 8 or 8 39 if it is not dissipated by the bombardment of ion implantation in the magnetic bubble memory device according to the present invention operation margin at the junction between the ion implantation transfer path and the permalloy transfer path is excellently improved as compared with that of the conventional magnetic bubble memory device more specifically minute magnetic bubbles of 1 u03bcm in diameter could be transferred without failing to traverse the junction under the biasing magnetic field in a wide range of 420 to 480 oe in contrast in the case of the conventional device the range of the biasing magnetic field in which magnetic bubbles of 1 u03bcm in diameter can be transferred was found to be about 420 to 450 oe which is remarkably narrow when compared with the range applicable in the device according to the present invention the above effect is demonstrated in fig6 the solid line in fig6 is the result for a device according to the invention in which was fabricated under the following conditions magnetic garnet layer ysmluga 3 fega 5 o 12 of 1 2 u03bcm thickness implantation mask az 1350 j resist of 1 u03bcm thickness having forwardly tapered cross section with about 14 u00b0 slope extending 4 u03bcm.