  Larger arrays of electron spin qubits require radical improvements in
fabrication and device uniformity. Here we demonstrate excellent qubit device
uniformity and tunability from 300K down to mK temperatures. This is achieved,
for the first time, by integrating an overlapping polycrystalline silicon-based
gate stack in an 'all-Silicon' and lithographically flexible 300mm flow.
Low-disorder Si/SiO$_2$ is proved by a 10K Hall mobility of $1.5 \cdot 10^4$
$cm^2$/Vs. Well-controlled sensors with low charge noise (3.6
$\mu$eV/$\sqrt{\mathrm{Hz}}$ at 1 Hz) are used for charge sensing down to the
last electron. We demonstrate excellent and reproducible interdot coupling
control over nearly 2 decades (2-100 GHz). We show spin manipulation and
single-shot spin readout, extracting a valley splitting energy of around 150
$\mu$eV. These low-disorder, uniform qubit devices and 300mm fab integration
pave the way for fast scale-up to large quantum processors.
