In this paper, the history and current development of the researches in chemical vapor deposition (CVD) of diamond films will be introduced first, followed by a brief description of the principles in CVD diamond synthesis. The stress will be focused on the great progress by the author in the areas of crystalline facet development, nucleation and heteroepitaxy of diamond using hot filament CVD (HFCVD) as follows:

(1) New results were obtained in the intensive experimental study on CVD diamond morphology development.

(2) Very low pressure nucleation method and electron emission enhanced nucleation method were developed, high density nucleation (up to the reported highest density) of diamond on mirror-polished single-crystal Si was achieved by these two methods. The difficulty of getting high density nucleation on mirror-polished Si was resolved.

(3) The difficulty of nucleation on thin Ti wafer and the embrittlement of Ti was resolved by very low pressure nucleation method.

(4) Heteroepitaxy of diamond on both Si(100) and Si(111) was achieved by the above two nucleation methods.

(5) The mechanism of diamond nucleation on hetero-substrate will be fully discussed, and a new general model will be established.

(6) Relatively large area direct epitaxy of diamond on Si(001) was observed by high resolution transmission electron microscopy (HRTEM) with a misorientation angle of 9^o. This is the best result in the world, proving the feasibility of direct diamond/Si epitaxy.

(7) Cases of 45^o rotation epitaxy of diamond on Si(001) were observed for the first time in the world. This is of great significance to the research in diamond/Si heteroepitaxial interface and its mechanism.