An MMC/SD core unit includes a PCBA in which all passive components and unpackaged IC chips are attached to a single side of a PCB opposite to the metal contacts. The IC chips include, for example, a controller chip and a flash memory chip, or a single-chip (combined controller/flash memory) chip. Multiple flash IC chips are optionally stacked to increase storage capacity. The IC chip(s) are attached to the PCB by wire bonding or other chip-on-board (COB) technique. The passive components are attached by conventional surface mount technology (SMT) techniques. A molded housing is then formed over the IC chips and passive components such that the device has a uniform thickness. The MMC/SD core unit is then inserted or otherwise mounted in an eternal casing to provide a finished MMC/SD device.