  The sensitivity of microwave kinetic inductance detectors (MKIDs) based on
coplanar waveguides (CPWs) needs to be improved by at least an order of
magnitude to satisfy the requirements for space-based terahertz astronomy. Our
aim is to investigate if this can be achieved by reducing the width of the CPW
to much below what has typically been made using optical lithography (> 1
{\mu}m). CPW resonators with a central line width as narrow as 300 nm were made
in NbTiN using electron beam lithography and reactive ion etching. In a
systematic study of quarter-wave CPW resonators with varying widths it is shown
that the behavior of responsivity, noise and power handling as a function of
width continues down to 300 nm. This encourages the development of narrow KIDs
using Al in order to improve their sensitivity.
