Ecotec is just a name that covers many engine families in GM's product lineup.
The all aluminum Family II Ecotecs have chain driven camshafts (2.2l-2.4l engines used in various cars since MY 2000).
The 1.8 Ecotec in the Cruze is a Family 1 engine, has a iron block and DOHC motors have aluminum heads (some SOHC motors have iron heads), and belt driven cams. It is the same motor used in the Saturn/Opel Astra, and for a few years, under Daewoo's D-Tec name.
The 1.4t is a Family 0 engine, again another Opel design phased in during the 1990's in Europe for small displacement tax friendliness. All have a iron block with aluminum heads and chain driven cam shafts.