I'll add my support for Comp-Tac, as well. I have a couple of all-leather holsters I use for OWB for time to time, but all my IWB and competition holsters are Comp-Tac. My go-to IWB choice is is the MTAC (formerly, the Minotaur).
Some interesting history. There are a number of makers of hybrid leather-Kydex holsters that imply, if not outright state, the original idea was theirs. The true story is that it originated about 11 years ago in conversations among Tucker (Tucker Gunleather), Rob Longenecker (also of Tucker Gunleather), and Gregg Garrett (who founded a holster company in Houston that subsequently became Comp-Tac Victory Gear). Collectively, they came up with the notion of melding quality leather and molded Kydex to maximize on the strengths of each: leather was strong yet supple, molded itself slightly to the contours of the wearer, and was comfortable against the body; Kydex was rigid and never collapsed after the gun was removed, could be molded with great precision to individual firearms, could be tension-adjusted for retention, and afforded a stable, repeatable draw time after time.
The result was Tucker's "The Answer." Tucker made the leather, Garrett made all the Kydex components. There was a naming contest in the spring of 2006 for the wholly new hybrid that included some headscratchers like the "Tool Shed." Thankfully, though, "The Answer" won out.
Garrett rapidly expanded production at Comp-Tac as the demand for competition Kydex holsters grew. Today, more competitors in the IDPA Nationals use Comp-Tac than any other brand of holster.
Gregg came out with the Comp-Tac CTAC: not exactly what we think of today as a leather/Kydex hybrid, it was a Kydex holster that used leather cross-struts to attach the Kydex belt clips to the body of the holster, allowing flex and give for comfort that Kydex alone couldn't provide. Then he rethought "The Answer," did some tweaking, and the Minotaur was born.
So if you see any claims about some holster maker or another being the first to place a Kydex body on leather backing and coming up with the idea of the hybrid, now you know.