  Silicon metal-oxide-semiconductor (MOS) spin qubits have become a promising
platform for quantum information processing, with recent demonstrations of
high-fidelity single and two-qubit gates. To move beyond a few qubits, however,
more scalable designs that reduce the fabrication complexity and electrode
density are needed. Here, we introduce a two-metal-layer MOS quantum dot device
in which tunnel barriers are naturally formed by gaps between electrodes and
controlled by adjacent accumulation gates. The accumulation gates define the
electron reservoirs and provide tunability of the tunnel rate of nearly 8.5
decades/V, determined by a combination of charge sensor electron counting
measurements and by direct transport. The valley splitting in the few-electron
regime is probed by magneto-spectroscopy up to a field of 6 T, providing an
estimate for the ground-state gap of 290 $\mu$eV. We show preliminary
characterization of a double quantum dot, demonstrating that this design can be
extended to linear dot arrays that should be useful in applications like
electron shuttling. These results motivate further innovations in MOS quantum
dot design that can improve the scalability prospects for spin qubits.
